Tuberculosis

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Tuberculosis

Introduction

Disease History, Characteristics, and Transmission

Scope and Distribution

Treatment and Prevention

Impacts and Issues

Primary Source Connection

BIBLIOGRAPHY

Introduction

Tuberculosis, often known as TB, is a disease caused by infection with the bacterium called Mycobacterium tuberculosis. A few other types of mycobacterium are capable of causing a tuberculosislike illness, but are only rarely encountered. Most commonly, the infection affects the lungs. However, along with the pulmonary form of tuberculosis, the infection can become extrapulmonary, affecting other parts of the body, including the central nervous system, kidneys, joints, spine, and skin.

In a tuberculosis infection, symptoms may be absent initially. Sometime later, in about 10% of those who are infected, this so-called latent tuberculosis, which cannot be spread from person to person, becomes active and more serious, killing up to 50% of those who are infected. The presence of the latent form of tuberculosis is especially dangerous in people whose immune systems are not functioning properly, such as those with acquired immunodeficiency syndrome (AIDS, also cited as acquired immune deficiency syndrome).

Disease History, Characteristics, and Transmission

Tuberculosis is an ancient disease. In about 400 BC, the Greek physician Hippocrates (460–377 BC) described a disease that is thought to have been tuberculosis. Then the disease was called phthisis, a name derived from the Greek word meaning “to waste away”. This description was apt, since, then, as now, a hallmark feature of tuberculosis is weight loss and physical deterioration that occurs over the often considerable length of time that the infection persists. In more recent times, the characteristic physical wasting associated with the disease led to its popular name—consumption.

A fragment of M. tuberculosis DNA was found in lung tissue from an Egyptian mummy approximately 3,000 years old. It has been argued that diseases like tuberculosis were unknown in South America until being introduced by European explorers hundreds of years ago. However, this may not be true, since preserved remains of people with tuberculosislike lung damage have been dated to hundreds of years before the time of Columbus. (There is no evidence that the Viking explorations, which pre-date Columbus, took them south of the equator.) It seems likely that tuberculosis may have been globally common even centuries ago.

The name tuberculosis was coined in 1839 by Johann Schönlein. At that time, the pathogen responsible for the disease had not been discovered. M. tuberculosis was finally identified in 1882 by Robert Koch (1843–1910), one of the pioneers of the study of bacteria (bacteriology). In 1890, Koch reported on the extraction of a bacterial protein from dead bacteria recovered from tuberculosis infections. The protein, which he called tuberculin, is still important as a means of detecting the presence of the bacteria. With the discovery and use of x rays at the end of the nineteenth century, the presence of the lung infection that is a consequence of the growth of M. tuberculosis was revealed. On x-ray images, the masses of bacteria that develop are seen as more opaque regions in the lungs.

Lung infection with M. tuberculosis results from inhaling droplets of moisture that contain the bacteria. Most commonly this occurs when someone who has the infection expels droplets from their lungs by coughing. The droplets, which tend to be 0.5–5 microns in diameter (a micron is a millionth of a meter) can contain more than 40,000 living M. tuberculosis bacteria. M. tuberculosis also can be transmitted in milk that has not been pasteurized to kill the bacteria. Symptoms of this form of tuberculosis, which is called active tuberculosis, include a feeling of tiredness, loss of weight, a fever that tends to occur during sleep, chills, and a cough that persists for weeks. The coughing can dislodge and expel sputum, which may be tinged with blood, as the infection can damage cells lining the lungs. In some people, the infection can spread beyond the lungs to other parts of the body. If not treated, this extrapulmonary tuberculosis is fatal in up to 50% of the cases. The extrapulmonary form cannot be spread from person to person.

Scope and Distribution

Tuberculosis is a common disease with a global distribution. About 30% of the world's population—some 2 billion people—have tuberculosis, according to the World Health Organization (WHO). The organization has estimated that new infections are occurring at the rate of one every second. In 2004, almost 15 million people had the active form of tuberculosis, according to the WHO, and about 1.7 million people died of the disease, most in developing countries. Nearly 9 million of these cases had developed during that year.

Some people are at increased risk for contracting tuberculosis. These include children, whose immune systems are not fully developed, and elderly people, whose immune function may have deteriorated. The immune system can also deteriorate due to diseases (for example, acquired immunodeficiency syndrome, or AIDS), poor nutrition, and the physical consequences of chronic alcohol or drug abuse. In addition, immune function may be deliberately suppressed in transplant patients to help minimize the chance of rejection of the transplanted organ. Health care providers may also be at risk of contracting tuberculosis, since they are exposed more frequently to people with the infection. Other risk factors include diabetes, various cancers, kidney disease, and abnormally low body weight.

While present in every country, tuberculosis can be especially prevalent in regions where health care is substandard and poverty affects the overall health of the inhabitants. Traditionally, this has been a more significant problem in underdeveloped and developing countries. However, even in the United States, increasing poverty has contributed to a resurgence of tuberculosis. More than 14,000 cases of tuberculosis were reported in the United States in 2004, according to the CDC.

Treatment and Prevention

The diagnosis of tuberculosis relies of the recognition of the symptoms and the detection of the infection. The presence of the lung infection can be visualized using a chest x ray. M. tuberculosis also can be detected, either by obtaining sputum samples and growing the organism or by isolating protein components of the bacterium. The latter test can be faster, since the bacterium can be difficult to grow in laboratory conditions. For example, the length of time for M. tuberculosis to grow and divide in the nutritionally rich conditions of a laboratory culture dish can be 16–20 hours, which is far longer than the 15–20 minutes required by the common intestinal bacterium Escherichia coli. Thus, identification of the tuberculosis bacterium by laboratory culturing can take days.

A well-known test for tuberculosis is called a skin test. In this test, the tuberculin protein from M. tuberculosis is injected just under the skin of the forearm. The development of redness and swelling at the injection site within several days indicates that the person has at least been exposed to the infection. The test does not necessarily show that the infection is active, and so is valuable in the detection of the latent form of tuberculosis.

In May 2005, the U.S. Food and Drug Administration approved the QuantiFERON -TB Gold test for use in the diagnosis of M. tuberculosis infection in the United States. The test detects the release of a compound called interferon-gamma from blood cells in those who have tuberculosis. The test has been approved as a replacement for the skin test, and to confirm the results of the skin test. As of 2007, the test is not widely available, and can still be beyond the budget of smaller health care centers.

In the past, the treatment of tuberculosis was associated with images of hospital wards filled with bedridden patients or images of people slowly recovering from the infection while at sanatoriums located in the countryside. Even into the 1960s, sanatoriums that were located in areas with clean, dry air were a popular part of treatment for tuberculosis.

Sanatoriums did aid recovery, but their usefulness was supplanted during the 1960s by the introduction of antibiotics that were effective against M. tuberculosis. The antibiotic treatment needs to be carried out for up to six months to be effective, in part because of the slow growth of the bacteria (many antibiotics are effective only on bacteria that are growing). It can be tempting to stop taking the antibiotics before the end of the prescribed period of treatment, since the patient begins to feel better after only a few weeks. But, as with other bacterial infections, discontinuing treatment prematurely is dangerous, since it can allow surviving bacteria to reestablish the infection. In fact, the surviving bacteria may be resistant to the antibiotics used, making treatment more difficult and more expensive.

The first few decades of the antibiotic therapy were resoundingly successful. Over 90% of tuberculosis infections were cured. However, in the early years of the twenty-first century, resistance to the antibiotics emerged and became more prevalent.

A tuberculosis vaccine does exist. It was developed during World War I (1914–1918) by French scientists Albert Calmette (1863–1933) and Camille Guérin, (1872–1961) and was first used in 1921. The vaccine uses a live, but weakened, strain of the bacterium Mycobacterium bovis. BCG (for Bacillus-Calmette-Guérin) is still the only vaccine for tuberculosis, although researchers are continuing to investigate new vaccine candidates.

The vaccine is not recommended for use in the United States by the CDC. This is due to a combination of factors—the relatively low number of cases of the disease in the United States, the vaccine's 80% success rate, and the risks associated with the use of live bacteria in a vaccine. Health care providers and others at higher risk to acquire the infection are vaccinated, however, as are people who have the multidrug-resistant form of tuberculosis. People who come to the United States from areas of the world where tuberculosis is prevalent are required to be examined for the presence of the active and latent forms of the infection and to be treated if necessary.

Efforts to develop new tuberculosis vaccines are ongoing. Several vaccine candidates have been developed using recombinant genetic techniques. These techniques involve splicing genetic material into an organism that can then ferry the recombined genetic material into animals or humans to generate antibodies to combat the infection. As of 2007, the U.S. National Institute of Allergy and Infectious Diseases and other agencies around the world continue to sponsor trials to evaluate the effectiveness and safety of the recombinant vaccines.

IN CONTEXT: EXTENSIVELY DRUG-RESISTANT TUBERCULOSIS (XDR TB)

In May 2007 a Centers for Disease Control and Prevention (CDC) investigation of a suspected case of Extensively Drug-Resistant Tuberculosis (XDR TB) made news headlines around the world and heightened public awareness of XDR TB. The case involved a U.S. citizen that the CDC publicly asserted had a “potentially infectious XDR TB who traveled to and from Europe on commercial flights between May 12 and May 24, (2007) and then re-entered the United States at the Canada-U.S. border via automobile.”

Because of the international travel implications, for the first time in more than 40 years, CDC issued a Federal isolation order under authority of the U.S. Public Health Service Act. Such are orders are rare because state and local health departments usually order isolation (in fact, in early June 2007, the Denver Health Authority Public Health Department issued an order that the patient be detained for treatment at the Denver area hospital where the patient had ultimately been transferred for treatment and so the federal order was lifted).

Although the patient was asymptomatic and physicians later stated that he did not appear to be highly infectious, the case came under intense media scrutiny. At the time of the printing of this book, many issues existed concerning the facts and timeline of events related to the case, including the investigation of how the patient may have initially contracted the disease and the events surrounding the response by a number of health and security agencies to his infection and subsequent travel. Intense media coverage was also fueled by initial disinformation about the nature of transmission, with reports failing to specify that transmission of the bacterium responsible usually takes prolonged contact.

The CDC states that Extensively drug-resistant tuberculosis (XDR TB) is “a relatively rare type of multidrug-resistant tuberculosis (MDR TB). It is resistant to almost all drugs used to treat TB, including the two best first-line drugs: isoniazid and rifampin. XDR TB is also resistant to the best second-line medications: fluoroquinolones and at least one of three injectable drugs (i.e., amikacin, kanamycin, or capreomycin).”

“Because XDR TB is resistant to the most powerful first-line and second-line drugs, patients are left with treatment options that are much less effective and often have worse treatment outcomes.”

“XDR TB is of special concern for persons with HIV infection or other conditions that can weaken the immune system. These persons are more likely to develop TB disease once they are infected, and also have a higher risk of death once they develop TB disease.”

“The risk of acquiring XDR TB in the United States appears to be relatively low. However, it is important to acknowledge the ease at which TB can spread. As long as XDR TB exists, the United States is at risk and must address the threat.”

SOURCE: Centers for Disease Control and Prevention, Division of Tuberculosis Elimination National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention

Impacts and Issues

Throughout history, tuberculosis has been a threat to health and life. For example, in the mid-nineteenth century, about 25% of all deaths were due to tuberculosis. The devastation caused to families and the economic consequences of the loss of so many wage-earners were immense. At that time, the disease was especially prevalent in children, adolescents, and young adults; whole generations of people were affected.

This situation changed during the 1940s with the introduction of antibiotics that were effective against M. tuberculosis. There was a steep drop in the number of cases of tuberculosis worldwide. This fueled optimism that the disease had been controlled. But, as with other bacterial diseases that were initially suppressed by anti-biotic therapy, this optimism was premature. Several factors have fueled the return of tuberculosis, including the increasing incidence of immunosuppressive diseases (primarily AIDS), the impact of growing gap in health care between the richer and poorer nations, and the emergence of a type of tuberculosis infection that is resistant to multiple antibiotics.

Currently, the impact of tuberculosis is most severe in the poorest regions of the world. For example, South Africa had the highest incidence of tuberculosis in the world in 2004, according to the WHO, and India had the most infections. WHO statistics show that more than 80% of the new cases of tuberculosis in 2004 were found among people living in Africa, Southeast Asia (including India), and the Western Pacific.

In other countries, including the United States, tuberculosis is less common and is mainly found in cities among the poor and homeless. In the United States, a program called Directly Observed Therapy (DOT) is being used by some states to help deal with the rising prevalence of tuberculosis. The program, which focuses on the poor and homeless in cities such as New York, involves direct meetings between the patient and a health care provider and the delivery of every scheduled dose of tuberculosis medication by that health care provider. DOT has been successful in reducing the number of reported cases of the disease.

DOT is also used in 182 other nations. It is estimated that this surveillance program, which relies on the microscopic detection of M. tuberculosis in blood samples, detected over 60% of the cases of tuberculosis worldwide in 2005.

In 1990, there were 7,537,000 tuberculosis cases worldwide, according to the WHO, with approximately 30,000 of those cases reported in the United States. The 14,097 reported cases in the United States in 2005 represent a 47% decline from 1990. However, in some states and among certain ethnic groups in the country, the prevalence of tuberculosis is still increasing. Furthermore, the situation elsewhere in the world is bleak. During the decade from 2000–2009, the WHO projects that 30 million people will die of tuberculosis. Since many cases are never reported, the actual death toll likely will be much higher.

In 2004, there were almost 9 million new cases of tuberculosis around the world, according to the WHO. Of these, 740,000 infections arose in people already infected with the human immunodeficiency virus (HIV). The immunocompromised condition of these patients makes it more likely that their cases of tuberculosis will be more serious, life threatening, and costly to treat.

IN CONTEXT: SCIENTIFIC, POLITICAL, AND ETHICAL ISSUES

The interplay of complex ethical and social considerations is also evident when considering the general rise of infectious diseases that sometimes occurs as an unintended side effect of the otherwise beneficial use of medications. Nearly half the world's population, for example, is infected with the bacterium causing TB (although for most people the infection is inactive) yet the organism causing some new cases of TB is evolving toward a greater resistance to the antibiotics that were once effective in treating TB. Such statistics also take on added social dimension when considering that TB disproportionately impacts certain social groups (the elderly, minority groups, and people infected with HIV).

The resurgence of tuberculosis has resulted in part from the increasing prevalence of immunodeficiency diseases, but also from a lack of attention to the control of tuberculosis. As with diseases such as polio, the early success in combating the disease led to complacency regarding control programs, with the result that the disease rebounded.

The emergence of antibiotic-resistant forms of M. tuberculosis is especially troubling. From 2000–2004, according to the CDC, 20% of tuberculosis cases in the United States were resistant to commonly used antibiotics and approximately 2% were resistant to the more potent and more expensive drugs employed as a next step. MDR-TB (multidrug-resistant TB) includes strains of tuberculosis that are resistant to at least two first-line drugs—isoniazid and rifampicin—used to treat TB.

Extremely drug-resistant tuberculosis (XDR-TB) is another emerging threat, according to the WHO. The disease is initially latent; when the symptoms appear and treatment is initiated, the resistance of the infection to virtually all antibiotics makes XDR-TB extremely difficult to treat.

As of 2007, identified XDR-TB is rare. Yet, the WHO estimates that in 2004 there were over 500,000 cases worldwide and that this number will rise in the coming years. The increased expense of treating XDRTB will become a significant issue for poorer nations. By 2015, according to the WHO, the treatment of tuberculosis will cost $650 million each year, in part due to elaborate airborne precautions in hospitals that include isolation rooms with specialized air exchanges and N-95 masks that can serve as a barrier for the extra-small bacteria that cause tuberculosis. More than $600 million will also be needed for programs aimed at curbing the spread of the multidrug-resistant bacteria. As of 2007, the funds budgeted by various governments around the world to battle tuberculosis total $250 million—$400 million less than the projected $650 million needed. In 2006, the WHO spearheaded the Stop TB Partnership, an initiative that aims to save 14 million lives by 2015, partly by encouraging nations worldwide to commit the needed money. The campaign also seeks to increase access to treatment for nations most in need, and to reduce the economic burden associated with the costs of tuberculosis health care and the work force losses due to the disease.

Primary Source Connection

The World Care Council (WCC), based in France, is a non-governmental organization (NGO) dedicated to mobilizing public and private forces together worldwide in the fight against AIDS, malaria, and tuberculosis. The Patients Charter for Tuberculosis Care, developed by the WCC, aims to empower people with tuberculosis by describing their rights and responsibilities regarding the disease. WCC intends for the charter to become the catalyst for effective collaboration between health providers, authorities, and persons with TB. The charter is the first global patient-powered standard for care.

The Patients’ Charter for Tuberculosis Care

The Patients’ Charter outlines the Rights and Responsibilities of People with Tuberculosis. It empowers people with the disease and their communities through this knowledge. Initiated and developed by patients from around the world, the Charter makes the relationship with health care providers a mutually beneficial one.

The Charter sets out the ways in which patients, the community, health providers, both private and public, and governments can work as partners in a positive and open relationship with a view to improving tuberculosis care and enhancing the effectiveness of the health care process. It allows for all parties to be held more accountable to each other, fostering mutual interaction and a ‘positive partnership’.

Developed in tandem with the International Standards for Tuberculosis Care to promote a ‘patient-centered’ approach, the Charter bears in mind the principles on health and human rights of the United Nations, UNESCO, WHO, Council of Europe, as well as other local and national charters and conventions.

The Patients Charter for Tuberculosis Care practices the principle of Greater Involvement of People with TB. This affirms that the empowerment of people with the disease is the catalyst for effective collaboration with health providers and authorities, and is essential to victory in the fight to stop TB. The Patients’ Charter, the first global ‘patient-powered’ standard for care, is a cooperative tool, forged from common cause, for the entire TB Community.

PATIENTS’ RIGHTS

You have the right to:

Care

The right to free and equitable access to tuberculosis care, from diagnosis through treatment completion, regardless of resources, race, gender, age, language, legal status, religious beliefs, sexual orientation, culture or having another illness.
The right to receive medical advice and treatment which fully meets the new International Standards for Tuberculosis Care, centering on patient needs, including those with MDR-TB or TB-HIV coinfections, and preventative treatment for young children and others considered to be at high risk.
The right to benefit from proactive health sector community outreach, education and prevention campaigns as part of comprehensive care programs.

Dignity

The right to be treated with respect and dignity, including the delivery of services without stigma, prejudice or discrimination by health providers and authorities.
The right to quality health care in a dignified environment, with moral support from family, friends and the community.

Information

The right to information about what health care services are available for tuberculosis, and what responsibilities, engagements, and direct or indirect costs, are involved.
The right to receive a timely, concise and clear description of the medical condition, with diagnosis, prognosis (an opinion as to the likely future course of the illness), and treatment proposed, with communication of common risks and appropriate alternatives.
The right to know the names and dosages of any medication or intervention to be prescribed, its normal actions and potential side-effects, and its possible impact on other conditions or treatments.
The right of access to medical information which relates to the patient's condition and treatment, and a copy of the medical record if requested by the patient or a person authorized by the patient.
The right to meet, share experiences with peers and other patients, and to voluntary counseling at any time from diagnosis through treatment completion.

Choice

The right to a second medical opinion, with access to previous medical records.
The right to accept or refuse surgical interventions if chemotherapy is possible, and to be informed of the likely medical and statutory consequences within the context of a communicable disease.
The right to choose whether or not to take part in research programs without compromising care.

Confidence

The right to have personal privacy, dignity, religious beliefs and culture respected.
The right to have information relating to the medical condition kept confidential, and released to other authorities contingent upon the patient's consent.

Justice

The right to make a complaint through channels provided for this purpose by the health authority, and to have any complaint dealt with promptly and fairly.
The right to appeal to a higher authority if the above is not respected, and to be informed in writing of the outcome.

Organization

The right to join, or to establish, organizations of people with or affected by tuberculosis, and to seek support for the development of these clubs and community based associations through the health providers, authorities, and civil society.
The right to participate as ‘stakeholders’ in the development, implementation, monitoring and evaluation of TB policies and programs with local, national and international health authorities.

Security

The right to job security after diagnosis or appropriate rehabilitation upon completion of treatment.
The right to nutritional security or food supplements if needed to meet treatment requirements.

PATIENTS’ RESPONSIBILITIES

You have the responsibility to:

Share Information

The responsibility to provide the health care giver as much information as possible about present health, past illnesses, any allergies and any other relevant details.
The responsibility to provide information to the health provider about contacts with immediate family, friends and others who may be vulnerable to tuberculosis or may have been infected by contact.

WORDS TO KNOW

ACTIVE INFECTION: An active infection is one which is currently producing symptoms or in which the infective agent is multiplying rapidly. In contrast, a latent infection is one in which the infective agent is present, but not causing symptoms or damage to the body, nor reproducing at a significant rate.

AIRBORNE PRECAUTIONS: Airborne precautions are procedures that are designed to reduce the chance that certain disease-causing (pathogenic) microorganisms will be transmitted through the air.

AIRBORNE TRANSMISSION: Airborne transmission refers to the ability of a disease-causing (pathogenic) microorganism to be spread through the air by droplets expelled during sneezing or coughing.

ANTIBIOTIC RESISTANCE: The ability of bacteria to resist the actions of antibiotic drugs.

LATENT INFECTION: An infection already established in the body but not yet causing symptoms, or having ceased to cause symptoms after an active period, is a latent infection.

Follow Treatment

The responsibility to follow the prescribed and agreed treatment plan, and to conscientiously comply with the instructions given to protect the patient's health, and that of others.
The responsibility to inform the health provider of any difficulties or problems with following treatment, or if any part of the treatment is not clearly understood.

Contribute to Community Health

The responsibility to contribute to community well being by encouraging others to seek medical advice if they exhibit the symptoms of tuberculosis.
The responsibility to show consideration for the rights of other patients and health care providers, understanding that this is the dignified basis and respectful foundation of the TB Community.

Show Solidarity

The moral responsibility of showing solidarity with other patients, marching together towards cure.
The moral responsibility to share information and knowledge gained during treatment, and to pass this expertise to others in the community, making empowerment contagious.
The moral responsibility to join in efforts to make the community TB Free.

World Care Council

WORLD CARE COUNCIL. “THE PATIENTS’ CHARTER FOR TUBERCULOSIS CARE.” 2006. AVAILABLE ONLINE AT< HTTP://WWW.WHO.INT/TB/PUBLICATIONS/2006/ISTC_CHARTER.PDF> (ACCESSED APRIL 10, 2007).