Tuberculosis

Definition

Tuberculosis (TB) is a potentially fatal contagious disease that can affect almost any part of the body but is mainly an infection of the lungs. It is caused by a bacterial microorganism, the tubercle bacillus or Mycobacterium tuberculosis. Although TB can be treated, cured, and can be prevented if persons at risk take certain drugs, scientists have never come close to wiping it out. Few diseases have caused so much distressing illness for centuries and claimed so many lives.

Description

Overview

Tuberculosis was popularly known as consumption for a long time. Scientists know it as an infection caused by M. tuberculosis. In 1882, the microbiologist Robert Koch discovered the tubercle bacillus, at a time when one of every seven deaths in Europe was caused by TB. Because antibiotics were unknown, the only means of controlling the spread of infection was to isolate patients in private sanitoria or hospitals limited to patients with TB—a practice that continues to this day in many countries. The net effect of this pattern of treatment was to separate the study of tuberculosis from mainstream medicine. Entire organizations were set up to study not only the disease as it affected individual patients, but its impact on the society as a whole. At the turn of the twentieth century more than 80% of the population in the United States were infected before age 20, and tuberculosis was the single most common cause of death. By 1938 there were more than 700 TB hospitals in this country.

Tuberculosis spread much more widely in Europe when the industrial revolution began in the late nineteenth century. The disease became widespread somewhat later in the United States, because the movement of the population to large cities made overcrowded housing so common. When streptomycin, the first antibiotic effective against M. tuberculosis, was discovered in the early 1940s, the infection began to come under control. Although other more effective anti-tuberculosis drugs were developed in the following decades, the number of cases of TB in the United States began to rise again in the mid-1980s. This upsurge was in part again a result of overcrowding and unsanitary conditions in the poor areas of large cities, prisons, and homeless shelters. Infected visitors and immigrants to the United Stateshave also contributed to the resurgence of TB. An additional factor is the AIDS epidemic. AIDS patients are much more likely to develop tuberculosis because of their weakened immune systems. There still are an estimated 8-10 million new cases of TB each year worldwide, causing roughly 3 million deaths.

High-risk populations

THE ELDERLY. Tuberculosis is more common in elderly persons. More than one-fourth of the nearly 23,000 cases of TB reported in the United States in 1995 developed in people above age 65. Many elderly patients developed the infection some years ago when the disease was more widespread. There are additional reasons for the vulnerability of older people: those living in nursing homes and similar facilities are in close contact with others who may be infected. The aging process itself may weaken the body's immune system, which is then less able to ward off the tubercle bacillus. Finally, bacteria that have lain dormant for some time in elderly persons may be reactivated and cause illness.

RACIAL AND ETHNIC GROUPS. TB also is more common in blacks, who are more likely to live under conditions that promote infection. At the beginning of the new millennium, two-thirds of all cases of TB in the United States affect African Americans, Hispanics, Asians, and persons from the Pacific Islands. Another one-fourth of cases affect persons born outside the United States. As of 2002, the risk of TB is still increasing in all these groups.

As of late 2002, TB is a major health problem in certain specific immigrant communities, such as the Vietnamese in southern California. One team of public health experts in North Carolina maintains that treatment for tuberculosis is the most pressing health care need of recent immigrants to the United States. In some cases, the vulnerability of immigrants to tuberculosis is increased by occupational exposure, as a recent outbreak of TB among Mexican poultry farm workers in Delaware indicates. Other public health experts are recommending tuberculosis screening at the primary care level of all new immigrants and refugees.

FLORENCE B. SEIBERT (1897–1991)

Florence Barbara Seibert was born on October 6, 1897, in Easton, Pennsylvania, the second of three children. She was the daughter of George Peter Seibert, a rug manufacturer and merchant, and Barbara (Memmert) Seibert. At the age of three she contracted polio. Despite her resultant handicaps, she completed high school, with the help of her highly supportive parents, and entered Goucher College in Baltimore, where she studied chemistryand zoology. She graduated in 1918, then worked under the direction of one of her chemistry teachers, Jessie E. Minor, at the Chemistry Laboratory of the Hammersley Paper Mill in Garfield, New Jersey. She and her professor, having responded to the call for women to fill positions vacated by men fighting in World War I, coauthored scientific papers on the chemistry of cellulose and wood pulps.

A biochemist who received her Ph.D. from Yale University in 1923, Florence B. Seibert is best known for her research in the biochemistry of tuberculosis. She developed the protein substance used for the tuberculosis skin test. The substance was adopted as the standard in 1941 by the United States and a year later by the World Health Organization. In addition, in the early 1920s, Seibert discovered that the sudden fevers that sometimes occurred during intravenous injections were caused by bacteria in the distilled water that was used to make the protein solutions. She invented a distillation apparatus that prevented contamination. This research had great practical significance later when intravenous blood transfusions became widely used in surgery. Seibert authored or coauthored more than a hundred scientific papers. Her later research involved the study of bacteria associated with certain cancers. Her many honors include five honorary degrees, induction into the National Women's Hall of Fame in Seneca Falls, New York (1990), the Garvan Gold Medal of the American Chemical Society (1942), and the John Elliot Memorial Award of the American Association of Blood Banks (1962).

LIFESTYLE FACTORS. The high risk of TB in AIDS patients extends to those infected by human immunodeficiency virus (HIV) who have not yet developed clinical signs of AIDS. Alcoholics and intravenous drug abusers are also at increased risk of contracting tuberculosis. Until the economic and social factors that influence the spread of tubercular infection are remedied, there is no real possibility of completely eliminating the disease.

Causes and symptoms

Transmission

Tuberculosis spreads by droplet infection. This type of transmission means that when a TB patient exhales, coughs, or sneezes, tiny droplets of fluid containing tubercle bacilli are released into the air. This mist, or aerosol as it is often called, can be taken into the nasal passages and lungs of a susceptible person nearby. Tuberculosis is not, however, highly contagious compared to some other infectious diseases. Only about one in three close contacts of a TB patient, and fewer than 15% of more remote contacts, are likely to become infected. As a rule, close, frequent, or prolonged contact is needed to spread the disease. Of course, if a severely infected patient emits huge numbers of bacilli, the chance of transmitting infection is much greater. Unlike many other infections, TB is not passed on by contact with a patient's clothing, bed linens, or dishes and cooking utensils. The most important exception is pregnancy. The fetus of an infected mother may contract TB by inhaling or swallowing the bacilli in the amniotic fluid.

Progression

Once inhaled, tubercle bacilli may reach the small breathing sacs in the lungs (the alveoli), where they are taken up by cells called macrophages. The bacilli multiply within these cells and then spread through the lymph vessels to nearby lymph nodes. Sometimes the bacilli move through blood vessels to distant organs. At this point they may either remain alive but inactive (quiescent), or they may cause active disease. Actual tissue damage is not caused directly by the tubercle bacillus, but by the reaction of the person's tissues to its presence. In a matter of weeks the host develops an immune response to the bacillus. Cells attack the bacilli, permit the initial damage to heal, and prevent future disease permanently.

Infection does not always mean disease; in fact, it usually does not. At least nine of ten patients who harbor M. tuberculosis do not develop symptoms or physical evidence of active disease, and their x-rays remain negative. They are not contagious; however, they do form a pool of infected patients who may get sick at a later date and then pass on TB to others. It is thought that more than 90% of cases of active tuberculosis come from this pool. In the United States this group numbers 10-15 million persons. Whether or not a particular infected person will become ill is impossible to predict with certainty. An estimated 5% of infected persons get sick within 12-24 months of being infected. Another 5% heal initially but, after years or decades, develop active tuberculosis either in the lungs or elsewhere in the body. This form of the disease is called reactivation TB, or post-primary disease. On rare occasions a previously infected person gets sick again after a later exposure to the tubercle bacillus.

Pulmonary tuberculosis

Pulmonary tuberculosis is TB that affects the lungs. Its initial symptoms are easily confused with those of other diseases. An infected person may at first feel vaguely unwell or develop a cough blamed on smoking or a cold. A small amount of greenish or yellow sputum may be coughed up when the person gets up in the morning. In time, more sputum is produced that is streaked with blood. Persons with pulmonary TB do not run a high fever, but they often have a low-grade one. They may wake up in the night drenched with cold sweat when the fever breaks. The patient often loses interest in food and may lose weight. Chest pain is sometimes present. If the infection allows air to escape from the lungs into the chest cavity (pneumothorax ) or if fluid collects in the pleural space (pleural effusion ), the patient may have difficulty breathing. If a young adult develops a pleural effusion, the chance of tubercular infection being the cause is very high. The TB bacilli may travel from the lungs to lymph nodes in the sides and back of the neck. Infection in these areas can break through the skin and discharge pus. Before the development of effective antibiotics, many patients became chronically ill with increasingly severe lung symptoms. They lost a great deal of weight and developed a wasted appearance. This outcome is uncommon today—at least where modern treatment methods are available.

Extrapulmonary tuberculosis

Although the lungs are the major site of damage caused by tuberculosis, many other organs and tissues in the body may be affected. The usual progression is for the disease to spread from the lungs to locations outside the lungs (extrapulmonary sites). In some cases, however, the first sign of disease appears outside the lungs. The many tissues or organs that tuberculosis may affect include:

• Bones. TB is particularly likely to attack the spine and the ends of the long bones. Children are especially prone to spinal tuberculosis. If not treated, the spinal segments (vertebrae) may collapse and cause paralysis in one or both legs.

• Kidneys. Along with the bones, the kidneys are probably the commonest site of extrapulmonary TB. There may, however, be few symptoms even though part of a kidney is destroyed. TB may spread to the bladder. In men, it may spread to the prostate gland and nearby structures.
• Female reproductive organs. The ovaries in women may be infected; TB can spread from them to the peritoneum, which is the membrane lining the abdominal cavity.
• Abdominal cavity. Tuberculous peritonitis may cause pain ranging from the vague discomfort of stomach cramps to intense pain that may mimic the symptoms of appendicitis.
• Joints. Tubercular infection of joints causes a form of arthritis that most often affects the hips and knees. The wrist, hand, and elbow joints also may become painful and inflamed.
• Meninges. The meninges are tissues that cover the brain and the spinal cord. Infection of the meninges by the TB bacillus causes tuberculous meningitis, a condition that is most common in young children but is especially dangerous in the elderly. Patients develop headaches, become drowsy, and eventually comatose. Permanent brain damage is the rule unless prompt treatment is given. Some patients with tuberculous meningitis develop a tumor-like brain mass called a tuberculoma that can cause stroke-like symptoms.
• Skin, intestines, adrenal glands, and blood vessels. All these parts of the body can be infected by M. tuberculosis. Infection of the wall of the body's main artery (the aorta), can cause it to rupture with catastrophic results. Tuberculous pericarditis occurs when the membrane surrounding the heart (the pericardium) is infected and fills up with fluid that interferes with the heart's ability to pump blood.
• Miliary tuberculosis. Miliary TB is a life-threatening condition that occurs when large numbers of tubercle bacilli spread throughout the body. Huge numbers of tiny tubercular lesions develop that cause marked weakness and weight loss, severe anemia, and gradual wasting of the body.

Diseases similar to tuberculosis

There are many forms of mycobacteria other than M. tuberculosis, the tubercle bacillus. Some cause infections that may closely resemble tuberculosis, but they usually do so only when an infected person's immune system is defective. People who are HIV-positive are a prime example. The most common mycobacteria that infect AIDS patients are a group known as Mycobacterium avium complex (MAC). People infected by MAC are not contagious, but they may develop a serious lung infection that is highly resistant to antibiotics. MAC infections typically start with the patient coughing up mucus. The infection progresses slowly, but eventually blood is brought up and the patient has trouble breathing. In AIDS patients, MAC disease can spread throughout the body, with anemia, diarrhea, and stomach pain as common features. Often these patients die unless their immune system can be strengthened. Other mycobacteria grow in swimming pools and may cause skin infection. Some of them infect wounds and artificial body parts such as a breast implant or mechanical heart valve.

Diagnosis

The diagnosis of TB is made on the basis of laboratory test results. The standard test for tuberculosis—which is the so-called tuberculin skin test—detects the presence of infection, not of active TB. Tuberculin is an extract prepared from cultures of M. tuberculosis. It contains substances belonging to the bacillus (antigens) to which an infected person has been sensitized. When tuberculin is injected into the skin of an infected person, the area around the injection becomes hard, swollen, and red within one to three days. Today skin tests utilize a substance called purified protein derivative (PPD) that has a standard chemical composition and is therefore is a good measure of the presence of tubercular infection. The PPD test is also called the Mantoux test. The Mantoux PPD skin test is not, however, 100% accurate; it can produce false positive as well as false negative results. What these terms mean is that some people who have a skin reaction are not infected (false positive) and that some who do not react are in fact infected (false negative). The PPD test is, however, useful as a screener. Anyone who has suspicious findings on a chest x ray, or any condition that makes TB more likely should have a PPD test. In addition, those in close contact with a TB patient and persons who come from a country where TB is common also should be tested, as should all healthcare personnel and those living in crowded conditions or institutions.

Because the symptoms of TB cover a wide range of severity and affected body parts, diagnosis on the basis of external symptoms is not always possible. Often, the first indication of TB is an abnormal chest x-ray or other test result rather than physical discomfort. On a chest x ray, evidence of the disease appears as numerous white, irregular areas against a dark background, or as enlarged lymph nodes. The upper parts of the lungs are most often affected. A PPD test is always done to show whether the patient has been infected by the tubercle bacillus. To verify the test results, the physician obtains a sample of sputum or a tissue sample (biopsy) for culture. Three to five sputum samples should be taken early in the morning. If necessary, sputum for culture can be produced by spraying salt solution into the windpipe. Culturing M. tuberculosis is useful for diagnosis because the bacillus has certain distinctive characteristics. Unlike many other types of bacteria, mycobacteria can retain certain dyes even when exposed to acid. This so-called acid-fast property is characteristic of the tubercle bacillus.

Body fluids other than sputum can be used for culture. If TB has invaded the brain or spinal cord, culturing a sample of spinal fluid will make the diagnosis. If TB of the kidneys is suspected because of pus or blood in the urine, culture of the urine may reveal tubercular infection. Infection of the ovaries in women can be detected by placing a tube having a light on its end (a laparoscope) into the area. Samples also may be taken from the liver or bone marrow to detect the tubercle bacillus.

One important new advance in the diagnosis of TB is the use of molecular techniques to speed the diagnostic process as well as improve its accuracy. As of late 2005, four molecular techniques are increasingly used in laboratories around the world. They include polymerase chain reaction to detect mycobacterial DNA in patient specimens; nucleic acid probes to identify mycobacteria in culture; restriction fragment length polymorphism analysis to compare different strains of TB for epidemiological studies; and genetic-based susceptibility testing to identify drugresistant strains of mycobacteria.

Treatment

Supportive care

In the past, treatment of TB was primarily supportive. Patients were kept in isolation, encouraged to rest, and fed well. If these measures failed the lung was collapsed surgically so that it could "rest" and heal. Today surgical procedures still are used when necessary, but contemporary medicine relies on drug therapy as the mainstay of home care. Given an effective combination of drugs, patients with TB can be treated at home as well as in a sanitorium. Treatment at home does not pose the risk of infecting other household members.

Drug therapy

Most patients with TB can recover if given appropriate medication for a sufficient length of time. Three principles govern modern drug treatment of TB:

• Lowering the number of bacilli as quickly as possible. This measure minimizes the risk of transmitting the disease. When sputum cultures become negative, this has been achieved. Conversely, if the sputum remains positive afterfive to six months, treatment has failed.
• Preventing the development of drug resistance. For this reason, at least two different drugs and sometimes three are always given at first. If drug resistance is suspected, at least two different drugs should be tried.
• Long-term treatment to prevent relapse.

Five drugs are most commonly used today to treat tuberculosis: isoniazid (INH, Laniazid, Nydrazid); rifampin (Rifadin, Rimactane); pyrazinamide (Tebrazid); streptomycin; and ethambutol (Myambutol). The first three drugs may be given in the same capsule to minimize the number of pills in the dosage. As of 1998, many patients are given INH and rifampin together for six months, with pyrazinamide added for the first two months. Hospitalization is rarely necessary because many patients are no longer infectious after about two weeks of combination treatment. Follow-up involves monitoring of side effects and monthly sputum tests. Of the five medications, INH is the most frequently used drug for both treatment and prevention.

Surgery

Surgical treatment of TB may be used if medications are ineffective. There are three surgical treatments for pulmonary TB: pneumothorax, in which air is introduced into the chest to collapse the lung; thoracoplasty, in which one or more ribs are removed; and removal of a diseased lung, in whole or in part. It is possible for patients to survive with one healthy lung. Spinal TB may result in a severe deformity that can be corrected surgically.

Prognosis

The prognosis for recovery from TB is good for most patients, if the disease is diagnosed early and given prompt treatment with appropriate medications on a long-term regimen. According to a 2002 Johns Hopkins study, most patients in the United States who die of TB are older—average age 62—and suffer from such underlying diseases as diabetes and kidney failure.

Modern surgical methods have a good outcome in most cases in which they are needed. Miliary tuberculosis is still fatal in many cases but is rarely seen today in developed countries. Even in cases in which the bacillus proves resistant to all of the commonly used medications for TB, other seldom-used drugs may be tried because the tubercle bacilli have not yet developed resistance to them.

Prevention

General measures

General measures such as avoidance of overcrowded and unsanitary conditions are also necessary aspects of prevention. Hospital emergency rooms and similar locations can be treated with ultraviolet light, which has an antibacterial effect.

Vaccination

Vaccination is one major preventive measure against TB. A vaccine called BCG (Bacillus Calmette-Guérin, named after its French developers) is made from a weakened mycobacterium that infects cattle. Vaccination with BCG does not prevent infection by M. tuberculosis but it does strengthen the immune system of first-time TB patients. As a result, serious complications are less likely to develop. BCG is used more widely in developing countries than in the United States. The effectiveness of vaccination is still being studied; it is not clear whether the vaccine's effectiveness depends on the population in which it is used or on variations in its formulation.

Prophylactic use of isoniazid

INH can be given for the prevention as well as the treatment of TB. INH is effective when given daily over a period of six to 12 months to people in high-risk categories. INH appears to be most beneficial to persons under the age of 25. Because INH carries the risk of side-effects (liver inflammation, nerve damage, changes in mood and behavior), it is important to give it only to persons at special risk.

KEY TERMS

Bacillus Calmette-Guérin (BCG)— A vaccine made from a damaged bacillus akin to the tubercle bacillus, which may help prevent serious pulmonary TB and its complications.

Mantoux test— Another name for the PPD test.

Miliary tuberculosis— The form of TB in which the bacillus spreads through all body tissues and organs, producing many thousands of tiny tubercular lesions. Miliary TB is often fatal unless promptly treated.

Mycobacteria— A group of bacteria that includes Mycobacterium tuberculosis, the bacterium that causes tuberculosis, and other forms that cause related illnesses.

Pneumothorax— Air inside the chest cavity, which may cause the lung to collapse. Pneumothorax is both a complication of pulmonary tuberculosis and a means of treatment designed to allow an infected lung to rest and heal.

Pulmonary— Referring to the lungs.

Purified protein derivative (PPD)— An extract of tubercle bacilli that is injected into the skin to find out whether a person presently has or has ever had tuberculosis.

Resistance— A property of some bacteria that have been exposed to a particular antibiotic and have "learned" how to survive in its presence.

Sputum— Secretions produced in the infected lung and coughed up. A sign of illness, sputum is routinely used as a specimen for culturing the tubercle bacillus in the laboratory.

Tuberculoma— A tumor-like mass in the brain that sometimes develops as a complication of tuberculous meningitis.

High-risk groups for whom isoniazid prevention may be justified include:

• close contacts of TB patients, including health care workers
• newly infected patients whose skin test has turned positive in the past two years
• anyone who is HIV-positive with a positive PPD skin test; Isoniazid may be given even if the PPD results are negative if there is a risk of exposure to active tuberculosis
• intravenous drug users, even if they are negative for HIV
• persons with positive PPD results and evidence of old disease on the chest x-ray who have never been treated for TB
• patients who have an illness or are taking a drug that can suppress the immune system
• persons with positive PPD results who have had intestinal surgery; have diabetes or chronic kidney failure; have any type of cancer; or are more than 10% below their ideal body weight

• people from countries with high rates of TB who have positive PPD results
• people from low-income groups with positive skin test results
• persons with a positive PPD reaction who belong to high-risk ethnic groups (African Americans, Hispanics, Native Americans, Asians, and Pacific Islanders)

Resources

BOOKS

Beers, Mark H., MD, and Robert Berkow, MD., editors. "Infectious Diseases Caused by Mycobacteria." In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

Pelletier, Kenneth R., MD. The Best Alternative Medicine, Part II, "CAM Therapies for Specific Conditions: Tuberculosis." New York: Simon & Schuster, 2002.

PERIODICALS

"Changing Patterns of New Tuberculosis Infections." Infectious Disease Alert August 15, 2002: 171-172.

"'Drug of Dreams' Preps for First Large-Scale Trail: Study to Begin this Year; Moxifloxacin to Debut Soon in Study 27." TB Monitor July 2002: 73.

Efferen, Linda S. "Tuberculosis: Practical Solutions to Meet the Challenge." Journal of Respiratory Diseases November 1999: 772.

Fielder, J. F., C. P. Chaulk, M. Dalvi, et al. "A High Tuberculosis Case-Fatality Rate in a Setting of Effective Tuberculosis Control: Implications for Acceptable Treatment Success Rates." International Journal of Tuberculosis and Lung Disease 6 (December 2002): 1114-1117.

"Guidelines Roll Out Two New Variations: Experts give Both a Thumbs Up." TB Monitor August 2002: 85.

Houston, H. R., N. Harada, and T. Makinodan. "Development of a Culturally Sensitive Educational Intervention Program to Reduce the High Incidence of Tuberculosis Among Foreign-Born Vietnamese." Ethnic Health 7 (November 2002): 255-265.

Kim, D. Y., R. Ridzon, B. Giles, and T. Mireles. "Pseudo-Outbreak of Tuberculosis in Poultry Plant Workers, Sussex County, Delaware." Journal of Occupational and Environmental Medicine 44 (December 2002): 1169-1172.

Moua, M., F. A. Guerra, J. D. Moore, and R. O. Valdiserri. "Immigrant Health: Legal Tools/Legal Barriers." Journal of Law and Medical Ethics 30, Supplement 3 (Fall 2002): 189-196.

"New Drugs Sought for Top Killer of Young Women Worldwide." Women's Health Weekly July 25, 2002: 20.

"Poor Patient Compliance Key to Drug Resistance in Tuberculosis." Pulse July 1, 2002: 18.

Stauffer, W. M., D. Kamat, and P. F. Walker. "Screening of International Immigrants, Refugees, and Adoptees." Primary Care 29 (December 2002): 879-905.

Su, W. J. "Recent Advances in the Molecular Diagnosis of Tuberculosis." Journal of Microbiology, Immunology, and Infection 35 (December 2002): 209-214.

ORGANIZATIONS

American Lung Association. 1740 Broadway, New York, NY 10019. (800) 586-4872. 〈http://www.lungusa.org〉.

National Heart, Lung, and Blood Institute (NHLBI). P. O. Box 30105, Bethesda, MD 20824-0105. (301) 592-8573. 〈www.nhlbi.nih.gov〉.

OTHER

New York State Department of Health. "Communicable Disease Fact Sheet."

Tuberculosis

Definition

Tuberculosis (TB) is a contagious and potentially fatal disease that can affect almost any part of the body but manifests mainly as an infection of the lungs. It is caused by a bacterial microorganism, the tubercle bacillus or Mycobacterium tuberculosis. TB infection can either be acute and short-lived or chronic and long-term.

Description

Although TB can be prevented, treated, and cured with proper treatment and medications, scientists have never been able to eliminate it entirely. The organism that causes tuberculosis, popularly known as consumption, was discovered in 1882. Because antibiotics were unknown, the only means of controlling the spread of infection was to isolate patients in private sanatoria or hospitals limited to patients with TB—a practice that continues to this day in many countries. TB spread very quickly and was a leading cause of death in Europe. At the turn of the twentieth century more than 80% of the people in the United States were infected before age 20, and tuberculosis was the single most common cause of death. Streptomycin was developed in the early 1940s and was the first antibiotic effective against the disease. The number of cases declined until the mid- to late-1980s, when overcrowding, homelessness, immigration, decline in public health inspections, decline in funding, and the AIDS epidemic caused a slight resurgence of the disease. The increase in TB in the United States peaked in 1992, and new cases reported in the United States continue to decrease as of 2004. Yet the number of cases in foreign-born individuals is rising, and the number of deaths from TB has been rising, making TB a leading cause of death from infection throughout the world. It is estimated that in the next 10 years 90 million new cases of TB will be reported, with the result of 30 million deaths, or about 3 million deaths per year.

Several demographic groups are at a higher risk of contracting tuberculosis. Tuberculosis is more common in elderly persons. More than one-fourth of the nearly 23,000 cases of TB in the United States in 1995 were reported in people above age 65. TB also is more common in populations where people live under conditions that promote infection, such as homelessness and injection drug use. In the late 1990s, two-thirds of all cases of TB in the United States affected African Americans, Hispanics, Asians, and persons from the Pacific Islands. Finally, the high risk of TB includes people who have a depressed immune system. High-risk groups include alcoholics, people suffering from malnutrition, diabetics, and AIDS patients — and those infected by human immunodeficiency virus (HIV) — who have not yet developed clinical signs of AIDS. TB is the number one killer of women of childbearing age worldwide. In poor countries, women with TB often don't know they have the disease until symptoms become severe.

As of late 2002, TB is a major health problem in certain immigrant communities, such as the Vietnamese in southern California. One team of public health experts in North Carolina maintains that treatment for tuberculosis is the most pressing healthcare need of recent immigrants to the United States. In some cases, the vulnerability of immigrants to tuberculosis is increased by occupational exposure, as a recent outbreak of TB among Mexican poultry farm workers in Delaware indicates. Other public health experts are recommending tuberculosis

screening at the primary care level for all new immigrants and refugees.

Causes & symptoms

Transmission

Tuberculosis spreads by droplet infection, in which a person breathes in the bacilli released into the air when a TB patient exhales, coughs, or sneezes. However, TB is not considered highly contagious compared to other infectious diseases. Only about one in three people who have close contact with a TB patient, and fewer than 15% of more remote contacts, are likely to become infected. Unlike many other infections , TB is not passed on by contact with a patient's clothing, bed linens, or dishes and cooking utensils. Yet if a woman is pregnant, her fetus may contract TB through blood or by inhaling or swallowing the bacilli present in the amniotic fluid.

Once inhaled, water in the droplets evaporates and the tubercle bacilli may reach the small breathing sacs in the lungs (the alveoli), then spread through the lymph vessels to nearby lymph nodes. Sometimes the bacilli move through blood vessels to distant organs. At this point they may either remain alive but inactive (quiescent), or they may cause active disease. The likelihood of acquiring the disease increases with the concentration of bacilli in the air, and the seriousness of the disease is determined by the number of bacteria with which a patient is infected.

Ninety percent of patients who harbor M. tuberculosis do not develop symptoms or physical evidence of the disease, and their x rays remain negative. They are not contagious; however, these individuals may get sick at a later date and then pass on TB to others. Though it is impossible to predict whether a person's disease will become active, researchers surmise that more than 90% of cases of active tuberculosis come from this pool of people. An estimated 5% of infected persons get sick within 12-24 months of being infected. Another 5% heal initially but, after years or decades, develop active tuberculosis. This form of the disease is called reactivation TB, or post-primary disease. On rare occasions a previously infected person gets sick again after a second exposure to the tubercle bacillus.

Pulmonary tuberculosis

Pulmonary tuberculosis is TB that affects the lungs, and represents about 85% of new cases diagnosed. It usually presents with a cough , which may or may not produce sputum. In time, more sputum is produced that is streaked with blood. The cough may be present for weeks or months and may be accompanied by chest pain and shortness of breath. Persons with pulmonary TB often run a low-grade fever and suffer from night-sweats. The patient often loses interest in food and may lose weight. If the infection allows air to escape from the lungs into the chest cavity (pneumothorax) or if fluid collects in the pleural space (pleural effusion), the patient may have difficulty breathing. The TB bacilli may travel from the lungs to lymph nodes in the sides and back of the neck. Infection in these areas can break through the skin and discharge pus.

Extrapulmonary tuberculosis

Although the lungs are the major site of damage caused by tuberculosis, many other organs and tissues in the body may be affected. Abut 15% of newly diagnosed cases of TB are extrapulmonary, with a higher proportion of these being HIV-infected persons. The usual progression of the disease is to begin in the lungs and spread to locations outside the lungs (extrapulmonary sites). In some cases, however, the first sign of disease appears outside the lungs. The many tissues or organs that tuberculosis may affect include:

• Bones. TB is particularly likely to attack the spine and the ends of the long bones.
• Kidneys. Along with the bones, the kidneys are probably the most common site of extrapulmonary TB. There may, however, be few symptoms even though part of a kidney is destroyed.
• Female reproductive organs. The ovaries in women may be infected; TB can spread from them to the peritoneum, which is the membrane lining the abdominal cavity.
• Abdominal cavity. Tuberculous peritonitis may cause pain ranging from the mild discomfort of stomach cramps to intense pain that may mimic the symptoms of appendicitis.
• Joints. Tubercular infection of joints causes a form of arthritis that most often affects the hips and knees.
• Meninges. The meninges are tissues that cover the brain and the spinal cord. Infection of the meninges by the TB bacillus causes tuberculous meningitis , a condition that is most common in young children and the elderly. It is extremely dangerous. Patients develop headaches, become drowsy, and eventually comatose. Permanent brain damage can result without prompt treatment.
• Skin, intestines, adrenal glands, and blood vessels. All these parts of the body can be infected by M. tuberculosis. Infection of the wall of the body's main artery (the aorta), can cause it to rupture with catastrophic results. Tuberculous pericarditis occurs when the membrane surrounding the heart (the pericardium) is infected and fills up with fluid that interferes with the heart's ability to pump blood.
• Miliary tuberculosis. Miliary TB is a life-threatening condition that occurs when large numbers of tubercle bacilli spread throughout the body. Huge numbers of tiny tubercular lesions develop that cause marked weakness and weight loss, severe anemia , and gradual wasting of the body.

Diagnosis

TB is diagnosed through laboratory test results. The standard test for tuberculosis infection, the tuberculin skin test, detects the presence of infection, not of active TB. Skin testing has been done for more than 100 years. In this process, tuberculin is an extract prepared from cultures of M. tuberculosis. It contains substances belonging to the bacillus (antigens) to which an infected person has been sensitized. When tuberculin is injected into the skin of an infected person, the area around the injection becomes hard, swollen, and red within one to three days.

Today skin tests utilize a substance called purified protein derivative (PPD) that has a standard chemical composition and is therefore a good measure of the presence of tubercular infection. The PPD test, also called the Mantoux test, is not always 100% accurate; it can produce false positive as well as false negative results. The test may indicate that some people who have a skin reaction are not infected (false positive) and that some who do not react are in fact infected (false negative). The PPD test is, however, useful as a screener and can be used on people who have had a suspicious chest x ray, on those who have had close contact with a TB patient, and persons who come from a country where TB is common.

Because of the multiple and varied symptoms of TB, diagnosis on the basis of external symptoms is not always possible. TB is often discovered by an abnormal chest x ray or other test result rather than by a claim of physical discomfort by the patient. After an irregular x ray, a PPD test is always done to show whether the patient has been infected. To verify the test results, the physician obtains a sample of sputum or a tissue sample (biopsy) for culture. In cases where other areas of the body might be infected, such as the kidney or the brain, body fluids other than sputum (urine or spinal fluid, for example) can be used for culture.

One important new advance in the diagnosis of TB is the use of molecular techniques to speed the diagnostic process as well as improve its accuracy. As of late 2002, four molecular techniques are increasingly used in laboratories around the world. They include polymerase chain reaction to detect mycobacterial DNA in patient specimens; nucleic acid probes to identify mycobacteria in culture; restriction fragment length polymorphism analysis to compare different strains of TB for epidemiological studies; and genetic-based susceptibility testing to identify drug-resistant strains of mycobacteria.

Treatment

Because of the nature of tuberculosis, the disease should never be treated by alternative methods alone. Alternative treatments can help support healing, but treatment of TB must include drugs and will require the care of a physician. Any alternative treatments should be discussed with a medical practitioner before they are applied.

Supportive treatments include:

• Diet. Nutritionists recommend a whole food diet including raw foods, fluids, and particularly pears and pear products (pear juice, pear sauce), since pears may help heal the lungs. Other helpful foods include fenugreek, alfalfa sprouts, garlic , pomegranate, and yogurt or kefir. Four tablespoons of pureed steamed asparagus at breakfast and dinner taken for a few months may also be helpful.
• Nutritional therapy. Nutritionists may recommend one or many of the following vitamins and minerals: vitamin A at 300,000 IU for the first three days, 200,000 IU for the next two days, then 50,000 IU for several weeks; beta-carotene at 25,000-50,000 IU; vitamin E at up to 1,000 IU daily unless the patient is a premenopausal woman with premenstrual symptoms; lipotrophic formula (one daily); deglycerolized licorice ; citrus seed extract; vitamin C ; lung glandular; essential fatty acids ; vitamin B complex ; multiminerals; and zinc.
• Herb therapy may use the tinctures of echinacea , elecampane, and mullein taken three times per day, along with three garlic capsules three times per day.
• Hydrotherapy may be used up to five times weekly. Dr. Benedict Lust , the founder of naturopathy, supposedly cured himself of tuberculosis by using hydrotherapy.
• Juice therapy. Raw potato juice, may be taken three times daily with equal parts of carrot juice plus one teaspoon of olive or almond oil, one teaspoon of honey, beaten until it foams. Before using the potato juice, starch should be allowed to settle from the juice.
• Topical treatment may use eucalyptus oil packs, grape packs or grain alcohol packs.

Professional practitioners may also treat tuberculosis using cell therapy , magnetic field therapy, or traditional Chinese medicine . Fasting may be undertaken, but only with a doctor's supervision.

Allopathic treatment

Drug therapy

Five drugs are most commonly used today to treat tuberculosis: isoniazid (INH), rifampin, pyrazinamide, streptomycin, and ethambutol. Of the five medications, INH is the most frequently used drug for both treatment and prevention. The first three drugs may be given in the same capsule to minimize and treat active TB the number of pills in the dosage. As of 1998, many patients are given INH and rifampin together for six months, with pyrazinamide added for the first two months. Hospitalization is rarely necessary because many patients are no longer infectious after about two weeks of combination treatment. A physician must monitor side effects and conduct monthly sputum tests. In 2002, the Centers for Disease Control (CDC) worked with medical organizations to release new guidelines that better individualize the drug regimens received by TB patients depending on their disease symptoms and severity. Many can now receive once-weekly doses of rifapentine in the continuation phase of treatment.

The first large scale trial of a new agent to treat TB began in 2002. The promising new drug, called moxifloxacin, may mean a shorter treatment course for TB sufferers in the near future. It will also be tested in combination with rifapentine, and researchers believe that using the drugs together will mean a less frequent dosing schedule for patients.

Drug resistance has become a problem in treating TB. When patients do not take medication properly or for long enough periods of time, the TB organisms may become drug resistant. This makes the patient vulnerable to further infection and allows the TB organism to develop resistance.

Surgery

Surgical treatment of TB may be used if medications are ineffective. There are three surgical treatments for pulmonary TB: pneumothorax, in which air is introduced into the chest to collapse the lung; thoracoplasty, in which one or more ribs are removed; and removal of a diseased lung, in whole or in part. It is possible for patients to survive with one healthy lung.

Expected results

The prognosis for recovery from TB is good for most patients, if the disease is diagnosed early and given prompt treatment with appropriate medications on a long-term regimen. According to a 2002 Johns Hopkins study, most patients in the United States who die of TB are older—average age 62—and suffer from such underlying diseases as diabetes and kidney failure.

Modern surgical methods are usually effective when necessary. Miliary tuberculosis is still fatal in many cases but is rarely seen today in developed countries. Even in cases in which the bacillus proves resistant to all of the commonly used medications, other seldom-used drugs may be tried because the tubercle bacilli have not yet developed resistance to them.

Prevention

Vaccination is widely used as a prevention measure for TB. A vaccine called BCG (Bacillus Calmette-Guérin, named after its French developers) is made from a weakened mycobacterium that infects cattle. Vaccination with BCG does not prevent infection, but it does strengthen the immune system of first-time TB patients. As a result, serious complications are less likely to develop. BCG is used more widely in developing countries than in the United States. Though the vaccine has been proven beneficial and fairly safe, its use is still controversial. It is not clear whether the vaccine's effectiveness depends on the population in which it is used or on variations in its formulation. Recently, efforts have been focused on developing a new vaccine.

Generally, prevention focuses on the prevention of transmission, skin-testing high-risk persons and providing preventive drug therapy to people at risk. Measures such as avoidance of overcrowded and unsanitary conditions are necessary aspects of prevention. Hospital emergency rooms and similar locations can be treated with ultraviolet light, which has an antibacterial effect.

INH is also given to prevent TB, and decreases the incidence of TB by about 60% over the life of the patient. INH is effective when taken daily for 6 to 12 months by people in high-risk categories who are under 35 years of age. About 1% of patients in preventive treatment develop toxicity. Because INH carries the risk of side effects (liver inflammation, nerve damage, changes in mood and behavior), it is important for its use to be monitored and to give it only to persons at special risk.

Unfortunately, failure of TB patients to complete the full course of their drugs adds to TB incidence and encourages development of drug-resistant strains of the disease. As scientists try to develop drugs that require shorter courses, physicians must work with patients to encourage compliance with their treatments. Even if symptoms go away, patients often have to continue their drug treatment for six months to be sure to stop the spread of their TB infection to others.

Resources

BOOKS

Burton-Goldberg Group. Alternative Medicine: The Definitive Guide. Puyallup, WA: Future Medicine Publishing, Inc., 1994.

"Infectious Diseases Caused by Mycobacteria." Section 13, Chapter 157 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 2001.

Merck Manual of Medical Information: Home Edition. Edited by Robert Berkow, et al. Whitehouse Station, NJ: Merck Research Laboratories, 1997.

Pelletier, Kenneth R., MD. The Best Alternative Medicine, Part II, "CAM Therapies for Specific Conditions: Tuberculosis." New York: Simon & Schuster, 2002.

Smolley, Lawrence A., and Debra F. Bryse. Breathe Right Now: A Comprehensive Guide to Understanding and Treating the Most Common Breathing Disorders. New York: W. W. Norton & Co., 1998.

PERIODICALS

"Changing Patterns of New Tuberculosis Infections." Infectious Disease Alert (August 15, 2002): 171–172.

"'Drug of Dreams' Preps for First Large-Scale Trail: Study to Begin this Year; Moxifloxacin to Debut Soon in Study 27." TB Monitor (July 2002): 73.

Efferen, Linda S. "Tuberculosis: Practical Solutions to Meet the Challenge." Journal of Respiratory Diseases (November 1999): 772.

Fielder, J. F., C. P. Chaulk, M. Dalvi, et al. "A High Tuberculosis Case-Fatality Rate in a Setting of Effective Tuberculosis Control: Implications for Acceptable Treatment Success Rates." International Journal of Tuberculosis and Lung Disease 6 (December 2002): 1114–1117.

"Guidelines Roll Out Two New Variations: Experts Give Both a Thumbs Up." TB Monitor (August 2002): 85.

Houston, H. R., N. Harada, and T. Makinodan. "Development of a Culturally Sensitive Educational Intervention Program to Reduce the High Incidence of Tuberculosis Among Foreign-Born Vietnamese." Ethnic Health 7 (November 2002): 255–265.

Kim, D. Y., R. Ridzon, B. Giles, and T. Mireles. "Pseudo-Out-break of Tuberculosis in Poultry Plant Workers, Sussex County, Delaware." Journal of Occupational and Environmental Medicine 44 (December 2002): 1169–1172.

Moua, M., F. A. Guerra, J. D. Moore, and R. O. Valdiserri. "Immigrant Health: Legal Tools/Legal Barriers." Journal of Law and Medical Ethics 30 (Fall 2002) (3 Suppl.): 189–196.

"New Drugs Sought for Top Killer of Young Women Worldwide." Women's Health Weekly (July 25, 2002): 20.

"Poor Patient Compliance Key to Drug Resistance in Tuberculosis." Pulse (July 1, 2002): 18.

Stauffer, W. M., D. Kamat, and P. F. Walker. "Screening of International Immigrants, Refugees, and Adoptees." Primary Care 29 (December 2002): 879–905.

Su, W. J. "Recent Advances in the Molecular Diagnosis of Tuberculosis." Journal of Microbiology, Immunology, and Infection 35 (December 2002): 209–214.

ORGANIZATIONS

American Lung Association. 432 Park Avenue South, New York, NY 10016. (800) LUNG-USA. <www.lungusa.org>.

National Heart, Lung, and Blood Institute (NHLBI). P. O. Box 30105, Bethesda, MD 20824-0105. (301) 592-8573. <www.nhlbi.nih.gov>.

OTHER

New York State Department of Health. Communicable Disease Fact Sheet. nyhealth@health.state.ny.us.

University of Wisconsin-Madison Health Sciences Libraries. "Pulmonary Medicine" Healthweb. http://www.biostat.wisc.edu/chslib/hw/pulmonar.

Amy Cooper

Teresa G. Odle

Rebecca J. Frey, PhD

tuberculosis is caused by the microorganism Mycobacterium tuberculosis, or tubercle bacillus. It was in 1882 that Robert Koch, among his many historic contributions to bacteriology, identified this as the cause of the disease, thus firmly establishing for the first time its infective nature. It has been estimated that one-third of the world's population has been infected by M. tuberculosis but only a minority, probably about 10%, go on to develop disease. Disease manifests in any number of ways, almost all of them chronic, involving practically any part of the body. The most common site involved is the lungs, where cavities are produced. When this occurs patients have a cough with sputum (which sometimes contains blood), weight loss, and fever. Those with this type of disease are the most infectious, because of the presence of the bacillus in the sputum. Animals also carry the disease; although Koch had denied the possibility, it was later realized that the bovine strain of the organism, Mycobacterium bovis, could cause human infection from cow's milk.

Historically, tuberculosis has long ranked among the most feared of diseases. Such dread is reflected in some of its alternative names, including John Bunyan's ‘Captain of all these Men of Death’, and Charles Dickens' ‘dread disease’ which capture something of the prevalence of the disease in their times. Other names conjure up images of the disease process: the term ‘consumption’ describes what happened to an individual — a progressive emaciation and wasting away. Still other terms, such ‘the King's Evil’ describe the lottery of survival (cure arising from the king's touch in medieval England). Yet tuberculosis is not only a disease of the past. Keats' ‘death warrant’ continues to haunt us. Historically tuberculosis conjures up romantic images of pale, wraith-like artists suffering lingering deaths. Literature, art, and music have all recorded and been transformed by the disease. Those who have succumbed to the disease form a veritable who's who of the artistic and political worlds and notions persist that those with artistic leanings are at greater risk from tuberculosis. As Susan Sontag noted in Illness as Metaphor, ‘tuberculosis was thought to come from too much passion, afflicting the reckless and sensual.’ Gradually, however, perceptions changed. In the US, for example, Katherine Ott noted in Fevered Lives that this ‘most flattering of all diseases’ of the 1870s was transformed, as awareness of the social associations grew in the 1880s, into a disease which was seen as the consequence of either acquired or inherited degeneracy and later came to mirror ethnic and racial fears and prejudices. Yet by the turn of the century the enthusiasm for pointing the finger at individual weaknesses was tempered by an increasing awareness that society's strictures were in part responsible. In truth, in past centuries tuberculosis was a frequent killer of people from all walks of life, not only the famous and infamous, the artistic and notorious. Those living in poverty and squalor were always most susceptible.

The sanatorium movement, which promoted wholesome rest and genteel exercise in pleasant surroundings, took off in the second half of the nineteenth century. In Britain, which borrowed the idea from Germany, the first sanatoria opened in the 1890s. Although many sanatoria in Europe catered for a select, affluent, cosmopolitan clientele (an image which persists in the popular imagination conjured up by establishments such as those at Davos in Switzerland), sanatorium treatment also, by the 1920s, became available for those unable to pay, and the average duration of stay shortened. However a decline in the sanatorium movement started with the onset of World War I and was hastened by the Depression which followed. Although there were still thousands of tuberculosis sufferers receiving care in sanatoria by the mid 1940s, the availability of effective drug treatment meant that they soon became obsolete. Removal of infectious sufferers from the community had contributed to a decrease in incidence of the disease, but for the patients in sanatoria or specialized hospitals there was no specific cure. Recovery was sometimes assisted by causing collapse of an infected lung by the introduction of air into the chest (artificial pneumothorax) or by an operation that ‘caved-in’ the overlying ribs (thoracoplasty).

The advent of drug treatment followed the discovery, by Selman Waksman in the US in 1944, that streptomycin was effective, and other drugs shortly followed. When chemotherapy from then on resulted in cure for most tuberculosis sufferers, contemporary commentators told stories largely of hope, of medicine's conquest of nature, and reflected less on societal hindrances to medicine's application. An optimistic faith in the benefits of science shone through such that it seemed merely a matter of time before this ancient scourge would be eradicated. At the time this optimism seemed well-founded: mortality rates in England and Wales, which had been falling by about 1% annually since the 1860s, declined dramatically from the mid 1940s. Death rates for respiratory tuberculosis in England and Wales were about 125/100 000 at the turn of the century, and by the 1960s had fallen to below 10/100 000. Preceding the advent of chemotherapy there had been improvements in social conditions and better identification of those with active disease, along with advances in bacteriology and in X-ray diagnosis. From the 1920s there were attempts to control bovine infection, first by certifying tuberculin tested (TT) herds, and later by heat treatment to kill bacteria in milk. Although this pasteurization had been considered as early as 1913, Britain lagged behind much of Europe and the US by more than a quarter of a century in putting it into consistent effect. A further preventative measure was the introduction in the 1950s of the BCG (Bacille Calmette Guérin) vaccination programme.

Despite the remarkable success in controlling tuberculosis in the West, the overriding optimism which followed the development of effective antituberculosis drugs in the 1940s and 1950s was somewhat premature. The disease continues to target those most marginalized and vulnerable. Each year more than 8 million people acquire tuberculosis (most of them in the developing world), and about 3 million die, including about 100 000 children, annually. In England and Wales there was concern as to why this should be, why Keats' death warrant should still be received by so many, given that we have had at our disposal for over fifty years drugs which are effective in curing the disease? The answer was known half a century ago.

‘Tuberculosis is a social disease, and presents problems that transcend the conventional medical approach. On the one hand, its understanding demands that the impact of social and economic factors on the individual be considered as much as the mechanisms by which tubercle bacilli cause damage to the human body. On the other hand, the disease modifies in a peculiar manner the emotional and intellectual climate of the societies that it attacks.’ Rene Dubos who, with his wife Jean, wrote these words in 1952, was one of the giants of twentieth-century medicine. As well as being a major figure in the development of antibacterial drugs in the US in the 1920s and 1930s, which led to the later successful antituberculous drugs, he was able, unlike so many, to see the place of tuberculosis in society and to recognize the limits of modern medicine. His words resonate through the years and perhaps are more pertinent now than ever. In 1993 the World Health Organization officially called the global threat of tuberculosis an ‘emergency’. New drug-resistant strains of the organism are spreading and modern medical approaches are failing to cure patients. In England and Wales there was a 20% increase in incidence of the disease between 1987 and 1990, weighted towards the underprivileged. Overcrowding, poverty, social alienation, increased incarceration rates in prisons, homelessness, and AIDS (the ‘deadly alliance’) are combining to overwhelm uncoordinated and under-resourced public health responses.

Perhaps nowhere have the consequences of contemporary public health failures been more obvious than in New York City. In the late 1980s and early 1990s an epidemic of this ancient disease killed hundreds of people, forcing politicians to rethink their approaches to those living on the margins of society, and provoking a response which has cost millions of dollars. As Rene Dubos knew all along, tuberculosis is as much a social and political disease as it is a medical condition.

Richard Coker

Bibliography

Coker, R. (2000). From chaos to coercion: detention and the control of tuberculosis. St Martins Press, New York.
Dormandy, T. (1999). The White Death: a history of tuberculosis. The Hambledon Press, London.
Ott, K. (1996). Fevered lives: tuberculosis in American culture since 1870. Harvard University Press, Cambridge MA.
Ryan, F. (1992). Tuberculosis: the greatest story never told. Swift publishers, Bromsgrove, Worcestershire.
Sontag, S. (1978). Illness as metaphor. Farrar, Straus and Giroux, New York.

Tuberculosis

Tuberculosis (TB) is an infectious disease of the lungs caused by the bacterium Mycobacterium tuberculosis. In the mid-nineteenth century, about one-fourth of the mortality rate was attributable to tuberculosis. It was particularly rampant in early childhood and young adulthood. Its presence was felt throughout the world, but by the 1940s, with the introduction of antibiotics , there was a sharp decline of cases in developed countries. For less-developed countries with poor public health structures, tuberculosis is still a major problem. Since 1989, however, there has been an increase in reported cases in economically advanced countries due mainly to immunosuppression associated with AIDS , and the emergence of antibiotic-resistant strains of TB.

The bacillus infects the lungs of those who inhale the infected droplets formed during coughing by an individual who has an active case of the disease. It can also be transmitted by unpasteurized milk, as animals can be infected with the bacteria . The disease is dormant in different parts of the body until it becomes active and attacks the lungs, leading to a chronic infection. Symptoms include fatigue, loss of weight, night fevers and chills, and persistent coughing with sputumstreaked blood. The virulent form of the infection can then spread to other parts of the body. Without treatment, the condition is eventually fatal.

Chest x rays and sputum examinations can show the presence of tuberculosis. Tuberculin, a purified protein taken from the tuberculosis bacilli, is placed under the skin of the forearm during a tuberculosis skin test. In two or three days if there is a red swelling at the site, the test is positive, and indicates TB infection, but not necessarily active TB disease. Early detection of the disease facilitates effective treatment to avoid the possibility of it becoming active later on.

Populations at risk of contracting TB are people with certain medical conditions or those using drugs for medical conditions that weaken the immune system . Others at risk are low-income groups, people from undeveloped countries with high TB rates, people who work in or are residents of long-term care facilities (nursing homes, prisons, hospitals), those who are significantly underweight, alcoholics, and intravenous drug users.

Traces of lesions from tuberculosis have been found in the lungs of ancient Egyptian mummies. The recent discovery of a Pre-Columbian mummy has resolved the debate on whether or not European explorers introduced the disease to the New World. Lung samples from a Peruvian woman who lived 500 years before Columbus discovered America show a lump that was identified as tuberculosis by DNA testing. Hippocrates, a Greek physician who lived from 460 to 370 B.C., described the disease. The Greek name for the disease was phthisis, derived from the verb phthinein, meaning to waste away. Tuberculosis was also called consumption because of the wasting away effects (notably, significant losses of weight over a period of time) of the disease.

In 1839, Johann Schonlein is credited with first labeling the disease tuberculosis. In 1882, the tubercle bacillus was discovered by Robert Koch , the German physician who pioneered the science of bacteriology. This landmark discovery was followed eight years later by his extraction of a protein from dead bacilli called tuberculin. This protein is still used to test for the presence of TB infection in a dormant or early stage. Another important diagnostic breakthrough came in 1895 with the discovery of Wilhelm Conrad Roentgen's x rays. The presence of TB lesions was detected on x rays.

Two twentieth century French scientists, Albert Calmette and Camille Guerin, developed a vaccine against tuberculosis from a weakened strain of bovine bacillus. Called BCG for Bacillus-Calmette-Guerin, this vaccine is the only one still in use although some scientists question its effectiveness. Despite doubts about the vaccine, it is still widely used, especially in TB endemic countries where other preventive measures are lacking. The U.S. Public Health Service's policy recommends testing and drug therapy for those infected instead of vaccination . The two factors responsible for this policy are the low incidence of TB in the United States and the doubts raised about BCG. The Centers for Disease Control and Prevention, (CDC), however, in its concern over the rising incidence of TB in the United States and the appearance of multidrug-resistant tuberculosis (MDR TB) which is difficult to treat, reexamined the TB vaccination issue, and released recommendations for its use in limited situations.

The CDC still recommends the use of skin tests and drug therapy as the most important measures in controlling the incidence of TB in the United States. Drug therapy is 90% effective in halting the infection. Since those vaccinated test positive with the skin test, a vaccination program would interfere with skin testing. Mass vaccination would risk giving up a simple test that provides an early warning. Relying on the drug treatment program to stop TB epidemics , however, has one major drawback. The drug therapy takes six months to a year before halting the infection. People infected are often among the homeless, poor, drug addicted, or criminal societies. Unless these people are carefully supervised to make sure they complete a regimen of drug therapy, it is difficult to effect a cure for the disease.

Throughout the nineteenth century and up until the 1960s, physicians sent their TB patients to sanatoriums which were rest homes located in mountains or semi-arid regions such as the American southwest. These locations were supposed to help the breathing process by providing clean and dry air. Physicians assumed that deeper, easier breathing in a work-free environment would help overcome the disease. Prior to the advent of antibiotics, these retreats were the only recourse for chronically ill tubercular patients. Although treatment in sanatoriums did help many, they were phased out before the 1960s, and replaced by antibiotic drug chemotherapy , which could be administered in either a hospital or home environment. Over 90% of TB patients can be cured by a combination of inexpensive antibiotics, but it is necessary they be used for a period of at least six months.

The impact of tuberculosis was evident in the nineteenth and early twentieth centuries in literature, art, and music. Puccini's opera, La Boheme, was created around the tragic death of the tubercular heroine, Mimi. Since TB often attacked the young, many poets, artists and musicians fell prey to the disease before they had a chance to fulfill their creative work. Among them, Amedeo Modigliani, John Keats, Frederic Chopin, and Anton Chekhov were claimed by the disease, along with millions of other young people during the period. In the United States, American playwright Eugene O'Neill was one of the fortunate few who did recover in a sanatorium and went on to write his plays. His early play, The Straw, written in 1919, dramatically shows what life was like in a sanatorium.

In the past, U.S. city and state governments were actively involved in regulations that controlled infected people from spreading the infection. At present, federal, state, and local agencies must again take a leading role in formulating a public policy on this complicated health problem. Several states are using a program called Directly Observed Therapy (DOT) to combat the rising incidence of TB. This program has met with considerable success in lowering reported cases of TB as much as 15% in New York City during the late 1990s.

DOT is offered at soup kitchens, clinics, hospitals, neighborhood health centers, and drug rehabilitation centers. Outreach workers enable those with TB to get help with the least amount of red tape. The wide array of medicines needed to treat the disease are made available, and ample funding has been provided from federal, state, and local agencies. Apartments are located for homeless patients and special provisions are made to help released prison inmates and those on parole. Guidelines for compassionate, supervised medical services are periodically reviewed for the successful implementation of the DOT program.

Despite such measures, the U.S. Department of Health and Human Services predicts tuberculosis, will spread further by the year 2005. In 1990, there were 7,537,000 TB cases worldwide. That number is expected to rise to 11,875,000 in 2005, a 58% increase. Most of the rise in rate is attributed to demographic factors (77%) while 23% accounts for the epidemiological factors, i.e., the rise in HIV infection. Approximately 30 million people around the world will die of TB from 2000 to 2009. These predictions are considered conservative because many cases of TB are never reported.

See also AIDS, recent advances in research and treatment; Bacteria and bacterial infection; Epidemiology, tracking diseases with technology; Public health, current issues

TUBERCULOSIS

Tuberculosis (TB), an infectious disease, has been present throughout ancient and modern history. TB rates in the United States are on the decline after a resurgence from 1985 to 1992. However, TB continues to be a major killer in much of the world. The implications of this epidemic are global, as travel and migration are now part of everyday life.

Although the cause, diagnosis, and treatment and prevention of TB are known, paradoxically, the disease continues to increase as a public health challenge. Caused by a bacterium called Mycobacterium tuberculosis, TB spreads via an airborne route from an infectious person coughing, sneezing, laughing, or singing. The bacteria infect mainly other individuals who have frequent and prolonged contact with a contagious TB case.

HISTORY

TB's existence dates back many centuries. There are references to TB in third-century b.c.e. Chinese and second-century b.c.e. Indian texts; Plato and Hippocrates wrote about it around 400 b.c.e. TB was commonly known as consumption in Europe, a cause of death for hundreds of thousands in the late eighteenth and nineteenth centuries. This is when TB in close groups was first observed and assumed to have a genetic cause, since it was commonly seen in families.

In 1882 Robert Koch's discovery of Mycobacterium tuberculosis led to the recognition of TB as an infectious disease. This discovery also led to interventions for interrupting transmission from person-to-person.

Beginning in the late 1880s, TB patients were treated in sanitoria with various modalities, including exposure to fresh air, exercise, and nourishment. About 50 percent of patients recovered or had long-term remission. However, as is known today, their "cure" was not due to the treatments administered but perhaps to self-healing mechanisms.

In the early twentieth century, public health interventions became key in controlling the spread of TB in the cities, where TB was most prevalent. For example, Herman M. Biggs, General Medical Officer of New York City, actively catalogued lists of TB patients and enforced isolation and environmental mechanisms to control TB, including the opening of a TB hospital to quarantine patients. Between 1914 and 1923, the Metropolitan Life Insurance Company conducted the "Framingham Tuberculosis Project" using community nurses to visit the homes of its clients to do assessments, teach health practices, and collect data for research and policy-making purposes. The project was in response to a high rate of TB-related mortality among Metropolitan customers. As a result, mortality rates for TB in the Metropolitan pool declined by 68 percent.

Beginning in 1921, the Bacille Calmette Guerin (BCG) vaccine was used to prevent TB. Still used in many parts of the world but not in the United States, the vaccine is not effective, except perhaps in infants. The discovery of streptomycin in 1943 brought drug treatment for TB. Between 1943 and 1952, two more TB drugs, para-amino-salicylic acid (PAS) and isoniazid (INH), were discovered. Sanitoria began to close in the early 1970s, as TB could be now be treated on an outpatient basis, as evidenced by success in the decrease in TB rates with combined drug treatment and infection-control mechanisms.

RESURGENCE

By 1985, there were 22,201 cases of TB in the United States, the lowest number recorded since national case reporting began in 1953. However, rates then began to increase, until in 1992 cases peaked at 26,673. The human immunodeficiency virus (HIV) epidemic was a major contributor, as its victims are at higher risk for developing active disease once infected with TB bacteria. Migration from countries with high rates of TB added to the number. Also, improper or inadequate drug treatment for TB has led to drug-resistant strains. Finally, medical education stressed TB to a lesser degree in academic curricula, and funding and interest in TB-control programs had dwindled with decreased cases. Most authorities feel that the latter reason was the most important.

Response to the American TB resurgence resulted in increased funding for TB control programs. This gave greater access to TB treatment through health departments. The health departments were responsible not only for treating cases, but for surveillance, outreach, case management, and treatment for those who had been exposed to infectious TB cases. Directly observed therapy short course (DOTS), the observation of the ingestion of medication, has now become the basis for the worldwide standard of TB care. DOTS includes five elements: government commitment to sustained TB-control activities; case detection and self-reporting to health services; standardized treatment regimen of six to eight months for at least all confirmed infectious cases, with directly observed treatment (DOT) for at least the initial two months; a regular, uninterrupted supply of all essential anti-TB drugs; and a standardized recording and reporting system that allows assessment of treatment results for each patient and of the TB control program overall. DOTS is presently available to 25 percent of the world's TB patients, but its acceptance is slowly increasing. There was also an increase in TB educational interventions via the public health sector and medical schools. New drug trials did not create new drugs but created variations on existing drugs and regimens. TB rates began to decrease again in 1994, and as of 1999, they were at an all-time low of 17,528 cases in the United States. Globally, there are still eight million new cases of TB annually with three million deaths. Clearly, even with the exemplary level of achievement domestically, TB cannot be controlled anywhere unless it is controlled everywhere.

THE FUTURE

Although one of the Healthy People 2010 goals calls for TB elimination from this country, the United States is still far from that goal. Many interventions need to be continued despite falling rates. For other communicable diseases, effective vaccine development and the advent of new drug therapies has been key to disease control approaching elimination. The best course for TB elimination is to develop a vaccine and new drugs while continuing surveillance, treating TB patients who may infect others, treating those who have been infected but are not yet active cases, increasing TB awareness among health professionals, and performing targeted testing for TB infection among high-risk populations. This combination of medical and public health practice can make TB elimination a reality.

Rajita R. Bhavaraju

Lee B. Reichman

(see also: Communicable Disease Control; Drug Resistance; Immunizations; Isolation )

Bibliography

Centers for Disease Control and Prevention (1995). Self-Study Modules on Tuberculosis. Atlanta, GA: Author.

—— (2000). Core Curriculum on Tuberculosis: What the Clinician Should Know, 4th edition. Atlanta, GA: Author.

Daniel, T. M. (1997). Captain of Death: The Story of Tuberculosis. Rochester, NY: University of Rochester Press.

Dublin, L. I. (1952). A Forty-Year Campaign against Tuberculosis: The Contribution of the Metropolitan Life Insurance Company. New York: Metropolitan Life Insurance Company.

Reichman, L. B. and Tanne J. H. (2001). Time Bomb: The Global Epidemic of Multidrug Resistant Tuberculosis. New York: McGraw Hill.

tuberculosis (TB), contagious, wasting disease caused by any of several mycobacteria. The most common form of the disease is tuberculosis of the lungs (pulmonary consumption, or phthisis), but the intestines, bones and joints, the skin, and the genitourinary, lymphatic, and nervous systems may also be affected.

There are three major types of tubercle bacilli that affect humans. The human type ( Mycobacterium tuberculosis ), first identified in 1882 by Robert Koch , is spread by people themselves. It is the most common one. The bovine type ( M. bovis ) is spread by infected cattle but is no longer a threat in areas where pasteurization of milk and the health of cattle are strictly supervised. The avian type ( M. avis ) is carried by infected birds but can occur in humans. The tubercle bacillus can live for a considerable period of time in air or dust. The most common means of acquiring the disease is by inhalation of respiratory droplets.

Course of the Disease

Tuberculosis of the lungs usually results in no or minimal symptoms in its early stages. In most persons the primary infection is contained by the body's immune system, and the lesion, called a tubercle, becomes calcified. In many the infection is permanently arrested. In others the disease may break out again and become active years later, usually when the body's immune defenses are low. Untreated, the infection can progress until large areas of the lung and other organs are destroyed. Symptoms of the disease include cough, sputum, bleeding from the lungs, fever, night sweats, loss of weight, and weakness.

Incidence

The incidence of tuberculosis of the lungs, the "white plague" that formerly affected millions of people, declined from the 1950s until 1984; sanatoriums were closed and routine screening was abandoned in the United States. Then, between 1984 and 1992, the incidence increased by 20%, chiefly because of immigration from countries where it is common and because of AIDS , which leaves people particularly vulnerable to the disease. Renewed efforts at control and advances in treatment have been rewarded with incidence declines each year, amounting to a total decline of 31% from 1992 to 1998.

Worldwide the outlook has been far less encouraging. In 1993 the World Health Organization (WHO) declared TB a global health emergency. Approximately one third of the world's population is infected, and an estimated 1.6 million die each year. The vast majority of new cases occur in sub-Saharan Africa. Spread of TB is especially rapid in areas with poor public health services and crowded living conditions. In homeless shelters and prisons, crowded conditions and inadequate treatment often go together. Areas where living conditions are disrupted by wars, famine, and natural disasters also are heavily affected.

Especially alarming has been the spread of drug-resistant strains of TB. By the late 1990s scientific experts and international health officials warned that drug-resistant strains were spreading faster than had been anticipated. Bacteria can survive and become drug resistant in patients whose treatment is not properly monitored and seen to completion. Multidrug resistant (MDR) TB strains are resistant to two or more of the commonly prescribed first-line drugs, while extensively drug resistant (XDR) strains are also resistant to three or classes of the more toxic second-line drugs. Some believe that unless major new treatment strategies are initiated in source countries, drug-resistant TB will eventually become epidemic even in areas with good control programs, such as Europe and America. In 2011, WHO estimated that there were more than 80,000 cases, many of them undiagnosed, of drug-resistant TB in Europe.

Diagnosis and Treatment

Diagnosis is made by a tuberculin skin test. It can be confirmed by X rays of the chest and sputum examination. Ideally, treatment begins after a skin test signals exposure but before active disease has developed. The treatment of choice for prevention and for active cases is the antimicrobial drug isoniazid (INH), available since 1956. In infected individuals it now is usually used in combination with other antituberculosis drugs such as rifampin, pyrazinamide, and ethambutol. Tuberculosis drugs have to be taken regularly, typically for 6 to 12 months. Many patients abandon their treatment when they feel better; similarly, preventive treatment is often abandoned because of the inconvenience. Such noncompliance is believed to be the main reason for the upsurge in drug-resistant strains of the TB bacilli, many of which are resistant to more than one drug. Drug-resistant TB is difficult to treat and has a much higher death rate; extensively drug resistant TB is especially worrisome because it can be essentially untreatable.

The combination drug rifater (rifampin, isoniazid, and pyrazinamide) has simplified drug administration. Directly observed treatment, where health-care workers watch patients take each dose of medicine, has proved effective in eliminating the problem of noncompliance in the United States, but monitoring has been less effective in many other parts of the world.

Prevention of Tuberculosis

Preventive measures include strict standards for ventilation, air filtration, and isolation methods in hospitals, medical and dental offices, nursing homes, and prisons. If someone is believed to have been in contact with another person who has TB, preventive antibiotic treatment may have to be given. Infected persons need to be identified as soon as possible so that they can be isolated from others and treated.

An antituberculosis vaccine, bacille Calmette-Guérin, or BCG vaccine, was developed in France in 1908. Although there is conflicting evidence as to its efficacy (it appears to be effective in 50% of those vaccinated), it is given to over 80% of the world's children, mostly in countries where TB is common; it is not generally given in the United States. Federal health officials in the United States have stated (1999) that a new vaccine is essential to TB prevention. It is hoped that the determination of the complete DNA (genome) sequence of Mycobacterium tuberculosis, achieved in 1998, will hasten the development of an effective vaccine.

Bibliography

See R. Dubos, The White Plague (1955); S. A. Waksman, The Conquest of Tuberculosis (1964).

Tuberculosis (TB), a disease with epidemiologic, socioeconomic, and cultural significance, was long believed to be a wasting condition caused by climate, poor diet, and bad habits, but since 1882, when the German bacteriologist Robert Koch identified the tubercle bacillus, it has been understood as an infectious bacterial disease. Tuberculosis can affect animals (particularly birds and cattle) as well as human beings. It most often attacks the lungs but can also strike bones and soft tissues; though infectious, it is not epidemic.

Tuberculosis, first known as phthisis or consumption, has been recognized as a leading cause of American deaths for as long as records have been kept. Anthropological evidence suggests that it was present in Native American populations before European contact. The missionaries, surveyors, and physicians who catalogued early American disease found it so prevalent that it seemed, as one surveyor wrote, “the direct offspring of the American soil and climate.”

Tuberculosis became particularly noteworthy during the nineteenth century, when it accounted for almost a quarter of all North American deaths. Early death from tuberculosis figured prominently in the literature and popular music of the era. The disease struck all classes of Americans, but not equally. Mid‐century physicians considered race a major determinant of TB and identified African‐American slaves as particularly susceptible. After the Civil War, TB came to be seen as a particular problem of cities, with “city habits, city houses, city occupations and city life” all cited as causes. Physicians often identified women, particularly millworkers, as especially at risk. In the early twentieth century, immigrants, Native American populations, and the rural poor were thought to be particularly vulnerable. As recently as 1960, the U.S. Public Health Service described tuberculosis as “the costliest of communicable diseases,” which reflected not only the expense of screening and treatment, but also the lost wages and dependency.

As late as the mid‐twentieth century, tuberculosis was difficult to treat. Late‐nineteenth and early‐twentieth century physicians commonly advocated the sanatorium treatment, comprising rest, good diet, and exercise that Dr. Edward Livingston Trudeau (1848–1915) pioneered at Adirondack Cottage Sanatorium at Saranac Lake, New York, in 1884. Prevention, through public‐health measures, including antispitting ordinances and the disposal of infected milk and meat, became a first line of defense after Koch identified the tubercle bacillus in 1882. Voluntary associations, especially the National Tuberculosis Association, launched major educational campaigns and funded research.

Koch's identification of the tubercle bacillus inspired hopes for a vaccine, and his highly touted “tuberculin cure” (1890) aroused great optimism. But while tuberculin proved a useful diagnostic agent, it had no curative properties BCG, a vaccine developed in France in 1924, from the bacillus Calmette‐Guérin, enjoyed widespread use around the world but not in the United States. Twentieth‐century American campaigns against TB relied on public‐health measures and the antibiotic streptomycin, developed by Salman Waksman in 1943. Long‐term chemoprophylaxis with the combination of bacteriostatic agents isoniazid and PAS (para‐aminosalicylic acid) became common after 1952.

After decades of low incidence and declining visibility, tuberculosis reemerged in the 1980s as a public‐health problem. This resurgence was variously attributed to immigration, the acquired immunodeficiency syndrome (AIDS) epidemic, drug‐resistant strains of TB, urban poverty, and the absence of an adequate health and social services net.
See also Biological Sciences; Medicine: From 1776 to the 1870s; Medicine: From the 1870s to 1945; Medicine: Since 1945; Urbanization

Bibliography

Barbara Bates , Bargaining for Life: A Social History of Tuberculosis, 1876–1938, 1992.
Sheila Rothman , Living in the Shadow of Death: Tuberculosis and the Social Experience of Illness in American History, 1994.
Georgina Feldberg , Disease and Class: Tuberculosis and the Shaping of Modern North American Society, 1995.

Georgina Feldberg

TUBERCULOSIS

The White Plague

Americans had lived in fear of tuberculosis for nearly three-quarters of a century by the 1950s. Because the disease is deadly and highly infectious, victims were isolated in special hospitals called sanatoriums, where at the beginning of the century, at least, they lived out their last days with other patients. The death rate from tuberculosis in 1950 was only 11 percent of what it was in 1900; still 33,633 people died from the disease that year. By 1955 the number of deaths from tuberculosis had been halved.

Good News

In 1956 the Annual Report of the National Tuberculosis Association contained good news: deaths from tuberculosis were down to sixteen thousand a year. For the first time in history, tuberculosis had fallen from the list of the top ten diseases rated by the number of deaths they cause. (By the end of the decade the death rate was down to just over ten thousand a year.) The report also contained the alarming fact that one American in three was infected with the bacillus that causes tuberculosis. The conclusion was that everyone had to be careful of developing the disease. Schoolchildren were tested periodically, and physicians acted swiftly with effective drugs when tuberculosis was suspected. As a resuit, by the middle of the decade new infections were most common among the down-and-out who did not receive adequate health care. One study conducted in Philadelphia showed the tuberculosis rate among inhabitants of skid row was eighteen times higher than among the general population

New Defenses

The most common form of tuberculosis, or TB, as the disease is known, affects the lungs. It is a bacterial disease that often results from unsanitary conditions or occupational hazards in such jobs as medical treatment. In the 1950s physicians tried to find cures and attempted to isolate victims to prevent its spread. The new antibiotic Terramycin, announced in 1950, joined streptomycin as a major weapon in the fight against the disease. The availability of other new medicines that stopped the progression of TB, coupled with the development of a blood test anounced in 1952 that accurately detected the disease in its early stage, marked the beginning of the end of the TB scare.

A PREGNANCY VACCINE

In 1950 longtime birth-control advocate Margaret Sanger enlisted Gregory Pincus, a reproductive biologist at the Worcester Foundation in Massachusetts, and his associates to work on what might be called a vaccine against pregnancy. After three years of research, the team focussed their attention on the effects of a synthetic form of the hormone estrogen, which seemed to control the rabbit population in the lab. In 1957 the G. D. Searle Company began marketing the synthetic hormone, called norethynodrel, but only as a treatment for menstrual cramps. There was no mention of its effectiveness at preventing pregnancy, a very controversial issue in the 1950s. Other companies had flatly refused to market medications for the purpose of birth control. For three years norethynodrel was quietly taken for either its stated purpose or its less-publicized effect of controlling pregnancy before the U.S. Food and Drug Administration finally in 1960 licensed several hormone preparations for contraceptive use.

Source:

James Bordley III and A. McGehee Harvey, Two Centuries of American Medicine (Philadelphia: Saunders, 1976), pp. 555-556.

Eradication

By the end of the 1950s, a controversial live-virus vaccine against TB, called BCG (for Bacillus developed by Albert Calmet and Camille Gudérin, scientists at the Pasteur Institute of Paris) was widely used, especially among medical personnel, in America. In a book, BCG Vaccination against Tuberculosis (Little, Brown, 1957) Dr. Roy Rosenthal, director of tuberculosis research at the University of Illinois, argued effectively for wider general use. A BCG shot cost fifty cents and provided long-term immunity against the disease. Sanatoriums were already being closed because people could be treated effectively at home, and the disease was considered well on its way to being eradicated.

Source:

Arthur J. Snider, "The Progress of Medicine," Science Digest (July 1955): 49;

"TB—and a Harsh Fact," Newsweek (7 October 1957): 100-101;

"Vaccination for TB," Time (26 March 1956): 69-70.

tuberculosis (TB) (tew-ber-kew-loh-sis) n. an infectious disease caused by the bacillus Mycobacterium tuberculosis and characterized by the formation of nodular lesions (tubercles) in the tissues. In the most common form of the disease (pulmonary t.) the bacillus is inhaled into the lungs where it sets up a primary tubercle and spreads to the nearest lymph nodes (the primary complex). Many people become infected but show no symptoms. Others develop a chronic infection and can transmit the bacillus by coughing and sneezing. Symptoms of the active disease include fever, night sweats, weight loss, and the spitting of blood. In some cases the bacilli spread from the lungs to the bloodstream, setting up millions of tiny tubercles throughout the body (miliary t.). Bacilli entering by the mouth, usually in infected cows' milk, set up a primary complex in abdominal lymph nodes, leading to peritonitis, and sometimes spread to other organs, joints, and bones (see Pott's disease). Tuberculosis is curable by various combinations of the antibiotics streptomycin, ethambutol, isoniazid (INH), rifampicin, and pyrazinamide. Preventive measures in the UK include the detection of cases by X-ray screening of vulnerable populations and vaccination with BCG vaccine. See also direct observed therapy.


www.hpa.org.uk/infections/topics_az/tb/menu.htm Explanation of TB from the Health Protection Agency

tuberculosis has been known in Ireland since early times, but it became a major scourge, especially in urban areas, in the late 19th and early 20th centuries. In 1906 tuberculosis caused nearly 16 per cent of all Irish deaths. Two sanatoriums were built in the 1890s, but attempts to make tuberculosis a notifiable disease were opposed by Irish politicians and tuberculosis remained a major killer throughout the 1920s and 1930s. The Women's National Health Association, established in 1907 by Lady Aberdeen, took the lead in attempts to combat the disease. However, it was only in the late 1940s that tuberculosis became a notifiable disease in Ireland, both north and south. At the same time a Tuberculosis Authority was established in Northern Ireland, which helped reduce the number of cases substantially during the 1950s, and Dr Noel Browne, the Irish health minister, launched a campaign that within a matter of a few years had brought tuberculosis under control in the Republic as well.

Elizabeth Malcolm

TUBERCULOSIS

DEFINITION

Tuberculosis (pronounced too-BUR-kyoo-LOH-siss), or TB, is a contagious disease of the lungs that can spread to other parts of the body and may be fatal. TB is caused by a microorganism known as the tubercle bacillus, or Mycobacterium tuberculosis. The disease can now be treated, cured, and prevented. However, scientists have never come closing to wiping it out and TB remains one of the most serious diseases worldwide.

DESCRIPTION

Some parts of the population are at higher risk of getting TB than others. For instance, tuberculosis is more common among elderly people. Typically, more than one-fourth of the TB cases reported in the United States occur among people above age sixty-five.

Elderly people are especially vulnerable for a number of reasons. First, the disease can take years to become active, so an older person may have gotten the disease earlier in life and only discovered it after it became active. Second, people who live in nursing homes and similar facilities are often in close contact with each other and the disease can spread more easily in such conditions. Third, the body's immune system becomes weaker as a person grows older and older people may find it more difficult to hold off an attack of the tubercle bacillus. The immune system is the body's network system for fighting off disease and infection.

Race also can be a factor in determining the risk of getting tuberculosis. TB occurs most commonly among African Americans. Other minorities are also at higher risk. Currently about two-thirds of all TB cases in the United States affect African Americans, Hispanics, Asians, and people from the Pacific Islands. Another one-fourth of cases in the United States affect people born outside the country.

People who are infected with the human immunodeficiency virus (HIV) are also at high risk for tuberculosis (see AIDS entry). HIV can damage a person's immune system, making it difficult for the body to fight off the TB bacterium. People who abuse alcohol and illegal drugs are also at high risk for the disease.

CAUSES

The most common method by which TB is transmitted is coughing or sneezing. When a person coughs or sneezes, he or she releases a fine mist of water droplets. If the person carries the tubercle bacillus, those droplets may contain thousands of the bacteria. A person nearby may inhale those water droplets and the bacteria they contain. The bacteria can then travel to that person's respiratory system and cause a new infection.

About a third of the people standing close to a person with TB are likely to develop the disease. Tuberculosis is not transmitted by contact with a person's clothing, bed linens, or dishes and cooking utensils. A fetus may become infected, however, by taking in bacilli from the mother.

Progression

The tubercle bacilli a person inhales may or may not cause tuberculosis. The human immune system has a variety of ways to capture and kill these bacteria. If the immune system is successful in doing so, the person will not become ill with TB.

Inhaled bacilli, however, may survive the immune system. They may travel throughout the body to organs other than the lungs. In some cases, the bacilli remain active enough to cause tuberculosis. In about 5 percent of all cases, a person develops tuberculosis within twelve to twenty-four months of being exposed to TB bacteria.

Tuberculosis: Words to Know

Bacillus Calmette-Guérin (BCG):

A vaccine made from weakened mycobacterium that infects cattle. It is used to protect humans against pulmonary tuberculosis and its complications.

Extrapulmonary:

Outside of the lungs.

Lesion:

Any change in the structure or appearance of a part of the body as the result of an injury or infection.

Mantoux test:

Another name for the PPD test, which is used to determine whether a person has been infected with the tuberculosis bacterium.

Miliary tuberculosis:

A form of tuberculosis in which the bacillus spreads throughout the body producing many thousands of tubercular lesions.

Mycobacteria:

A group of bacteria that includes Mycobacterium tuberculosis, the bacterium that causes tuberculosis.

Pericardium:

the membrane surrounding the heart.

Pulmonary:

Relating to the lungs.

Purified protein derivative (PPD):

A substance injected beneath the skin to see whether a person presently has or has ever had the tubercle bacillus.

Sputum:

Secretions produced inside an infected lung. When the sputum is coughed up it can be studied to determine what kinds of infection are present in the lung.

Vaccine:

A substance that causes the body's immune system to build up resistance to a particular disease.

By contrast, less than 10 percent of all people who inhale the tubercle bacillus actually become ill. The rest develop no symptoms of the disease and have negative X rays for the disease. In such cases, the disease is said to be inactive. The bacilli remain alive in cells, but they are not active enough to actually cause disease. They may become more active later in life, however.

In such cases, a person may become ill with tuberculosis long after being exposed to the TB bacteria.

Scientists believe that anywhere from ten to fifteen million Americans are carrying inactive tubercle bacilli in their bodies.

SYMPTOMS

Cases of tuberculosis are often classified as to whether they occur in the lung (pulmonary tuberculosis) or elsewhere in the body (extrapulmonary tuberculosis). Pulmonary tuberculosis is often confused with other diseases of the respiratory system. A person with TB may feel slightly sick or develop a mild cough. The person may also cough up small amounts of greenish or yellow sputum in the morning; the sputum can sometimes contain blood.

Other symptoms include a low-grade fever, a loss of interest in food, mild chest pain, difficulty in breathing, and night sweats. If the TB bacilli travel from the lungs to the lymph nodes, which help fight off illness, other symptoms, such as skin infections, may develop. More serious symptoms can also develop, including severe weight loss. Modern antibiotics, however, can prevent patients from reaching that stage of the disease.

THE FIGHT AGAINST TUBERCULOSIS THEN AND NOW

In the mid-seventeenth and eighteenth centuries, many countries underwent an Industrial Revolution. Because of inventions such as the steam engine, cities saw an increase of factory and industrial jobs, and more and more people moved from farms in the country to work in the city. Once there, workers often lived in very close contact with relatives and neighbors. Under those crowded and unsanitary conditions, tuberculosis was able to spread easily among the population.

Before scientists knew what caused tuberculosis, the disease was commonly referred to as consumption.

Until recently, there was no way of treating the disease. Instead, people with "consumption" were isolated in private hospitals or sanitariums. The purpose of isolation was to prevent the disease from spreading to uninfected people. Because of this practice, the study of tuberculosis also became separated from other fields of medicines. Entire organizations were created to study the disease, its effects on patients, and its impact on society as a whole.

In 1885 the German microbiologist Robert Koch discovered the tubercle bacillus and showed that this microorganism was responsible for tuberculosis. At the time, TB was responsible for one out of every seven deaths that occurred in Europe.

At the turn of the twentieth century, more than 80 percent of all Americans had been infected with TB before the age of twenty. Most of these people did not become ill since their bodies were able to fight off the disease. However, tuberculosis was still the most common cause of death among Americans. Even as late as 1938 there were more than seven hundred TB hospitals in the United States.

The first step in the conquest of TB occurred with the discovery of streptomycin in the early 1940s. Streptomycin is an antibiotic that kills the tubercle bacillus. Eventually, a number of other anti-tuberculosisdrugs were developed and progress was made in overcoming the disease.

By 1985 a conference was held to develop plans to eliminate tuberculosis forever. The number of cases of TB had been dropping for many years and many experts thought that TB was no longer going to be a serious disease. Then, in the late 1980s, the number of TB cases began to rise, both in the United States and around the world. Why did this change come about? At least five factors are thought to play a role in the return of TB as a major health problem:

• Education. Efforts to educate people about the disease may have lessened as the perceived threat of TB decreased.
• AIDS/HIV epidemic. As HIV weakens a person's immune system, a patient can become more prone to developing infectious diseases, such as tuberculosis.
• Living conditions. People who are poor, or homeless, or who live in crowded and unsanitary conditions may also develop weakened immune systems, or increase their chances of coming in contact with the disease. Drug users often have weakened immune systems as well. As the number of people in these categories increases, so does the rate of tuberculosis.
• Population movement. The increased movement of people across national boundaries is another factor. When people take vacations, conduct business, or move to new countries, they may take TB with them.
• Drug Resistance. TB bacteria have become resistant to many of the drugs once used to treat the disease.

Experts estimate that eight to ten million new cases of tuberculosis develop worldwide every year. The disease is thought to be responsible for about three million deaths annually. While there are various ways to fight the disease, if root problems, such as homelessness, poverty, drug use, and drug resistance are not solved, tuberculosis may once again become a major health problem.

Extrapulmonary Tuberculosis

Some of the tissues and organs in which extrapulmonary tuberculosis may appear are the following:

• Bones. TB is particularly likely to infect the spine and the ends of the long bones. Children are especially susceptible to spinal tuberculosis. If the disease is not treated, it may cause collapse of the vertebrae and paralysis in one or both legs.
• Kidneys. The kidneys are another common location for extrapulmonary tuberculosis. Although there are few signs of TB kidney infections, the disease may spread to the bladder, the prostate gland (in men), and other nearby organs and tissues.
• Female reproductive organs. In women, TB bacilli may spread to the ovaries and the peritoneum (pronounced per-i-tuh-NEE-uhm), the membrane lining the abdominal cavity.
• Abdominal cavity. Peritonitis (pronounced per-i-tuh-NIE-tiss), infection of the peritoneum, produces symptoms similar to those of stomach cramps and appendicitis (see appendicitis entry).
• Joints. Infection of the joints results in a form of arthritis (see arthritis entry) that most commonly affects the hips and knees. Less commonly, the wrist, hand, and elbow joints may become painful and inflamed.
• Meninges (pronounced mu-NIHN-jeez). The meninges are tissues that cover the brain and the spinal cord. Infection of the meninges by the TB bacillus causes tubercular meningitis (see meningitis entry). This condition is most common among children, but most dangerous among the elderly. Symptoms of tubercular meningitis include headaches and drowsiness. If left untreated, a person with tubercular meningitis may lose consciousness and suffer permanent brain damage.
• Skin, intestines, adrenal glands, and blood vessels. The TB bacterium can infect all of these body parts. One serious result can occur when the body's main artery, the aorta, becomes infected. The infection may cause the aorta to rupture, resulting in the person's death. Infection of the pericardium, the membrane surrounding the heart, can cause pericarditis (pronounced per-i-kar-DIE-tiss) which interferes with the heart's ability to pump blood.
• Miliary tuberculosis. Miliary tuberculosis occurs when very large numbers of tubercle bacilli spread throughout the body. Huge numbers of tiny lesions (pronounced LEE-zhuns) develop throughout the body causing severe anemia, weakness, weight loss, and wasting. Lesions are any change in the structure or appearance of a part of the body as the result of an injury or infection.

DIAGNOSIS

The first sign of tuberculosis may be the presence of one or more of the symptoms described. For example, someone who experiences persistent cold-like systems might seek medical advice. In such cases, a medical worker can take samples of a person's sputum. The sputum can then be cultured (grown and studied) to look for tubercle bacilli. Standard chemical tests are available for the detection of these bacilli.

Body fluids other than sputum can also be collected and cultured. For example, studies of the urine will indicate whether the kidneys or bladder have been infected.

Perhaps the most common warning sign for tuberculosis is an abnormal chest X ray. The X ray of a person with pulmonary tuberculosis will show numerous white, irregular areas against a dark background and/or enlarged lymph nodes. Chest X rays are recommended for anyone who has close contact with a TB patient. For example, health care workers who have contact with people at risk for the disease should have regular chest X rays.

The most common method for diagnosing TB has traditionally been a tuberculin skin test. Tuberculin consists of antigens, substances produced by an M. tuberculosis culture. In a tuberculin skin test, these antigens are injected beneath the skin. If TB bacteria are present, the injection becomes hard, swollen, and red within one to three days. This change is generally a good indication that infection has occurred.

Today, skin tests generally use a substance called purified protein derivative (PPD). The PPD test, also called the Mantoux test, tends to provide more accurate results than the traditional tuberculin test. However, both false positives and false negatives do occur. A false positive is a test that suggests infection has occurred when it really has not. A false negative is a test that shows that no infection has occurred when, in fact, it actually has.

TREATMENT

In the past, treatment of tuberculosis was primarily supportive. Patients were kept in isolation, away from the healthy population. They were encouraged to rest and to eat well. If these measures failed, surgery was used. Today, surgical procedures are used much less often. Instead, drug therapy has become the primary means of treatment. Patients with TB can now safely rest at home; they pose no threat to other members of the household.

Drug Therapy

Drugs provide the most effective treatment for TB patients. Three principles govern the use of drug treatment for tuberculosis:

• First, the number of bacilli must be lowered as quickly as possible. By so doing, the risk of transmitting the disease to other people is reduced.
• Second, efforts must be made to prevent the development of drug resistance. If a person develops a resistance to a drug, it will no longer be helpful in curing the disease. As a result, most patients are given a combination of two or three different drugs at first.
• Third, drug treatment must be continued to prevent reoccurrence of the disease.

Five drugs are used today to treat tuberculosis. They are isoniazid (also known as INH; pronounced eye-suh-NY-uh-zid, trade names Laniazid, Nydrazid); rifampin (pronounced ry-FAM-puhn, trade names Rifadin, Rimactane); pyrazinamide (pronounced pir-uh-ZIN-uh-mide, trade name Tebrazid); streptomycin (pronounced strep-tuh-MYS-uhn); and ethambutol (pronounced eth-AM-byoo-tol, trade name Myambutol). The first three drugs are often combined into a single capsule so that patients have fewer pills to take.

Surgery

Surgery is sometimes used to treat tuberculosis when medication is not effective. One form of surgery involves the introduction of air into the chest. This procedure causes the lung to collapse. In a second procedure, one or more ribs may be removed. A third procedure involves the removal of all or part of a diseased lung. Other forms of surgery may be used in cases of extrapulmonary tuberculosis.

PROGNOSIS

The prognosis for recovery from TB is good for most patients. The key to success is early diagnosis of the disease followed by a careful program of medication. The most serious form of tuberculosis, miliary tuberculosis, is still fatal in many cases, but it is seldom seen in developed countries today.

PREVENTION

Probably the most important form of prevention is to reduce the over-crowded and unsanitary conditions in which many people live. This action reduces the risk of transmitting TB from infected to uninfected people.

Vaccinations

The Bacillus Calmette-Guérin vaccine (BCG) is available for use against tuberculosis. A vaccine is a substance that causes the body's immune system to build up resistance to a particular disease. BCG is made from a type of mycobacterium that infects cattle. When injected into humans, it stimulates the immune system against M. tuberculosis. The vaccine, however, is more effective in some groups of people than in others. Scientists are conducting studies to better understand why the vaccine is not as effective in some parts of the population.

Preventative Use of Isoniazid

Isoniazid can be used to prevent the development of TB as well as to treat it. There is no point in giving the drug to everyone, however, since most people never come into contact with someone who has tuberculosis, so their risk of infection is small. However, some people encounter TB carriers often. These people can benefit from taking isoniazid on a regular basis. The treatment involves receiving a dose of isoniazid once every six to twelve months.

Among the groups that should consider the use of isoniazid as a preventative against TB are: health care workers who have contact with TB patients; people who are HIV positive; intravenous drug users; anyone who has had positive PPD results and abnormal chest X rays in the past; people with depressed immune systems; and members of high-risk groups who have had positive PPD tests.

FOR MORE INFORMATION

Books

Hyde, Margaret O. Know About Tuberculosis. New York: Walker & Company, 1994.

Landau, Elaine. Tuberculosis. New York: Franklin Watts, Inc., 1995.

Silverstein, Alvin, Virginia Silverstein, and Robert Silverstein. Tuberculosis. Hillside, NJ: Enslow Publishers, Inc., 1994.

Organizations

National Institute of Allergy and Infectious Diseases. Building 31, Room 7A-50, 31 Center Drive, MSC 2520, Bethesda, MD 20892–2520. http://www.niaid.nih.gov.

tuberculosis (TB) Infectious disease caused by the bacillus Mycobacterium tuberculosis. It most often affects the lungs (pulmonary tuberculosis), but may involve the bones and joints, skin, lymph nodes, intestines, and kidneys. One-third of the world's population is infected, and up to 5% of those infected eventually develop TB. Poor urban living conditions have lead to a resurgence of the disease in the USA and much of Europe, where previously it had been in decline. The BCG vaccine against tuberculosis developed in the 1920s and the first effective treatment drug, streptomycin, became available in 1944. However, the bacillus shows increasing resistance to drugs and some strains are multi-resistant.

Tuberculosis

What Is Tuberculosis?

Is TB Common?

How Is TB Spread?

What Are the Signs and Symptoms of TB?

How Do Doctors Diagnose and Treat TB?

What Are Some Complications of TB?

Can TB Be Prevented?

Resources

Tuberculosis (too-ber-kyoo-LO-sis) is a bacterial infection that primarily attacks the lungs but can spread to other parts of the body.

KEYWORDS

for searching the Internet and other reference sources

Consumption

Directly observed therapy (DOT)

Lung diseases

Mantoux test

MDR tuberculosis

Mycobacterium tuberculosis

PPD test

Tuberculin skin test

What Is Tuberculosis?

A germ known as Mycobacterium (my-ko-bak-TEER-e-um) tuberculosis causes tuberculosis (TB). Being infected with the bacterium and actually having the disease tuberculosis are very different. When most people breathe in M. tuberculosis bacteria, the immune system quickly seals off the invading bacteria in the lungs and protects the body from illness. These people are said to have latent, or inactive, TB (also called primary infection): their bodies carry the germs, but they have no symptoms and are not contagious. However, latent TB germs sometimes escape the immune system’s barriers and cause disease.

HIV and TB: A Lethal Combination

One of the reasons for the surge in TB cases in the 1980s was the rapid increase in the number of HIV cases. Because HIV/AIDS weakens the immune system, patients who have HIV/AIDS are at high risk for contracting TB when the germ first is breathed in. Approximately 11 million people around the globe are infected with both HIV and TB. TB is more likely to spread to other areas of the body in people with HIV, and multidrug-resistant (MDR) TB is much more dangerous in these patients. TB infection in patients who have HIV/AIDS can be cured if found and treated early.

When a person’s immune system is no longer able to contain the bacteria, or if latent TB activates for other reasons, tuberculosis disease, or active TB, develops (also called secondary infection). Patients may feel sick quickly or develop symptoms gradually over weeks or months, and they may be highly contagious until treated. If TB travels through the blood to invade organs outside the lungs, it is known as disseminated TB. Many organs and bones, including the brain, pericardium (sac surrounding the heart), kidneys*, gastrointestinal* tract, and spine, can become involved and be damaged by the infection.

*kidneys

are the pair of organs that filter blood and remove waste products and excess water from the body in the form of urine.

*gastrointestinal

(gas-tro-in-TES-tih-nuhl) means having to do with the organs of the digestive system, the system that processes food. It includes the stomach, intestines, and other organs involved in digestion, including the liver and pancreas.

Is TB Common?

TB is one of the most common causes of death due to infection in the world. About 2 million people around the world die from TB each year. In the nineteenth century, TB was a major cause of death, especially among young children. Drugs to treat the disease were first developed in the 1940s, and they dramatically lowered the number of TB cases over the next few decades. Unfortunately, TB began to resurface in the 1980s, but the number of cases has been declining in recent years. Between 10 and 15 million Americans are believed to have latent TB.

There are several reasons why TB made a comeback:

• HIV/AIDS* has weakened the immune systems of many people, increasing their likelihood of contracting TB.

*AIDS ,

or acquired immunodeficiency (ih-myoo-no-dih-FIH-shen-see) syndrome, is an infection that severely weakens the immune system; it is caused by the human immunodeficiency virus (HIV).

• Increased numbers of malnourished, poor, or homeless people live in crowded, unclean conditions and are vulnerable to infection.
• TB bacteria become more resistant to medications when patients do not take the drugs as prescribed. Multidrug-resistant (MDR) TB is difficult to treat and spreads easily.
• Immigration to the United States from countries with high rates of TB has increased.

TB can affect anyone, but it is most common among immigrants from countries with high levels of TB and people whose immune systems are weak because of chronic* illness, medications that affect the immune system, infancy, old age, poor nutrition, unclean or crowded living areas (including prisons), alcoholism, or intravenous* (IV) drug use.

*chronic

(KRAH-nik) means continuing for a long period of time.

*intravenous

(in-tra-VEE-nus) means within or through a vein. For example, medications, fluid, or other substances can be given through a needle or soft tube inserted through the skin’s surface directly into a vein.

In the twenty-first century, the number of TB cases is falling once again in the United States thanks to effective public health measures, including finding contacts of anyone known to have TB so that they may be treated as well, and directly observing that patients take medication as prescribed.

How Is TB Spread?

Active TB involving the lungs is highly contagious if untreated. Like the flu, TB is spread through the air. When a person with active TB sneezes, coughs, or talks closely to others, bacteria are passed through tiny drops of fluid from the mouth and nose that are unknowingly breathed in by others. Spending lots of time in close quarters with a person who has untreated active TB is the most common way to become infected. A brief encounter with an infected person usually does not spread TB. Touching an infected person or his or her belongings does not put a person at risk for TB. Within a few weeks of the start of effective treatment, patients are no longer contagious.

What Are the Signs and Symptoms of TB?

People with latent TB have no symptoms, but they need to be aware of signs of active TB. Active TB may begin with mild symptoms like those of the flu but quickly worsens. Possible symptoms include:

• cough that lasts a long time
• coughing up blood or lots of mucus*

*mucus

(MYOO-kus) is a thick, slippery substance that lines the insides of many body parts.

• chest pain
• loss of appetite and weight loss
• weakness and exhaustion
• fever and chills
• night sweats

If TB spreads to other parts of the body, additional serious symptoms may occur, depending on the organs involved.

How Do Doctors Diagnose and Treat TB?

TB infection is detected through a skin test known as the Mantoux test or PPD (purified protein derivative) test. A tiny amount of tuberculin (too-BER-kyoo-lin) substance, a protein taken from M. tuberculosis, is injected into the skin of an arm. A few days later a health professional will check to see if a bump has formed at the site of the injection. If the bump is wider than a certain size (for most people, 10 to 15 millimeters or a half inch), the patient most likely has been infected by TB bacteria; this is known as a positive skin test.

Next, a doctor will determine if the patient has active TB through a physical exam and by asking about symptoms and people the patient has had close contact with recently. The doctor may hear “crackles” when listening to the lungs with a stethoscope if a person has active TB. A chest X ray will be done, and samples of sputum*, blood, and urine may be tested. It can take weeks to confirm a diagnosis, although treatment can begin based on the skin test results and the person’s symptoms.

*sputum

(SPYOO-tum) is a substance that contains mucus and other matter coughed out from the lungs, bronchi, and trachea.

MDR TB

Multidrug-resistant tuberculosis (MDR TB) occurs when TB patients stop taking their prescribed medications or do not take them as directed. Patients often stop taking the drugs when they begin to feel better or to avoid side effects. However, TB bacteria can survive inside the body for several months during treatment and are ready to spring back into activity when the medication disappears.

Symptoms return with a vengeance, and infected people become highly contagious again, putting those close to them at risk. In MDR TB, germs become stronger than the antibiotics, making the drugs less effective. Patients with MDR TB need special medications, but they may not work as well. In addition, patients can spread this highly dangerous form of the disease to others.

One way to fight this problem is through directly observed therapy (DOT). In DOT, patients must take their medications regularly in the presence of a health professional. Home visits by health professionals to supervise the taking of medications or free transportation and meals often are provided to encourage patients to take part in this type of program.

Both latent and active TB can be cured if patients closely follow their doctors’ orders. Antibiotics must be taken by mouth every day for 6 months to 1 year. Hospitalization and isolation may be required in the early stages of active disease for people who are highly contagious or who have severe symptoms. Patients must continue to take medications even if they begin to feel better. If they do not, the germs that are still in the body can cause symptoms to return and drugs to stop working properly due to the development of MDR TB.

Once treatment begins, TB symptoms disappear within a few weeks. People with TB can lead normal, active lives while taking their medications over the course of several months.

What Are Some Complications of TB?

Complications of TB include:

• side effects of the drugs used to treat TB, which range from mild to severe
• lung damage and difficulty breathing
• damage to other organs from disseminated TB
• development of MDR TB
• other bacterial infections
• death

Can TB Be Prevented?

The Centers for Disease Control and Prevention recommends that people at high risk for TB (such as those with HIV infection or immigrants from areas with high rates of TB) get a skin test yearly so that treatment can begin immediately if they are found to have TB.

A TB vaccine* is given to infants and toddlers in countries with high levels of the disease. The vaccine is not commonly used in the United States because it does not always work and it may cause a positive skin test, making it more difficult to detect true TB infection.

*vaccine

(vak-SEEN) is a preparation of killed or weakened germs, or a part of a germ or product it produces, given to prevent or lessen the severity of the disease that can result if a person is exposed to the germ itself. Use of vaccines for this purpose is called immunization.

Practical prevention tips include:

• avoiding close contact with people infected with TB until they are no longer contagious
• wearing a special type of facemask (called a respirator) that can prevent the spread of TB if close contact with someone who has TB is necessary

See also

AIDS and HIV Infection

Pneumonia

Public Health

Resources

Organizations

American Lung Association, 61 Broadway, 6th Floor, New York, NY 10006. The American Lung Association offers information about tuberculosis and other diseases that affect the lungs at its website. Telephone 212-315-8700 http://www.lungusa.org

National Institute of Allergy and Infectious Diseases (NIAID), Building 31, Room 7A-50, 31 Center Drive MSC 2520, Bethesda, MD 20892. The NIAID, part of the National Institutes of Health, posts information about tuberculosis at its website.

http://www.niaid.nih.gov

U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton Road, Atlanta, GA 30333. The CDC is the U.S. government authority for information about infectious and other diseases. It provides information about tuberculosis at its website.

Telephone 800-311-3435 http://www.cdc.gov

World Health Organization (WHO), Avenue Appia 20, 1211 Geneva 27, Switzerland. WHO posts information about tuberculosis and tracks TB cases worldwide on its website.

Telephone 011-41-22-791-2111 http://www.who.int

tu·ber·cu·lo·sis / təˌbərkyəˈlōsis; t(y)oō-/ (abbr.: TB) • n. an infectious disease characterized by the growth of nodules (tubercles) in the tissues, esp. the lungs, caused chiefly by the bacterium Mycobacterium tuberculosis.

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