POLIO

DEFINITION

Polio (pronounced POH-lee-oh) is a serious disease caused by a virus called the poliovirus. The full medical name for the disease is poliomyelitis (pronounced POH-lee-oh-mi-uh-LI-tis). In its severest form, polio causes paralysis of the muscles of the legs, arms, and respiratory (breathing) system.

DESCRIPTION

The poliovirus causes most of its infections in the summer and fall. At one time, summer epidemics of polio were common and greatly feared.

The poliovirus primarily affects younger children. But it can also infect older children and adults. Poor hygiene and crowded living conditions encourage the spread of the poliovirus.

Paralysis is the most serious symptom of polio. Only about 1 percent to 2 percent of those infected with the virus are paralyzed, however. Risk factors for paralysis include older age, pregnancy, problems with the immune system, a recent tonsillectomy, and a recent episode of very strenuous exercise.

Polio: Words to Know

Brain stem:

A mass of nervous tissue that connects the main part of the brain to the spinal cord.

Epidemic:

The widespread occurrence of a disease over a large geographic area for an extended period of time.

Paralysis:

The inability to move one's muscles.

CAUSES

Poliovirus is transmitted through saliva and feces. It is passed on when people do not wash their hands after eating or using the bathroom. Once a person is infected with the virus, it can remain in the mouth and throat for about three weeks. It then travels to the intestine. It can remain in the intestine for up to eight weeks.

Inside the intestine, the virus multiplies rapidly. It may invade the lymphatic (pronounced lim-FAT-ic) system. The lymphatic system consists of organs and tissues that help protect a person against disease. The virus eventually enters the bloodstream. It can then pass to the central nervous system (the brain and spinal cord). The virus can also pass directly into nerves. It can then travel along a nerve to the brain.

SYMPTOMS

About 90 percent of those infected with poliovirus have mild or no symptoms. These symptoms include a low fever, fatigue, headache, sore throat, and nausea and vomiting. These symptoms usually last two or three days. People with these symptoms are still infectious and can pass the disease on to other people.

Another 10 percent of those infected with the virus experience more serious symptoms, including severe headache and pain and stiffness of the neck and back. The stiffness is caused when the tissues around the spinal cord and brain become inflamed. These symptoms usually disappear after several days. The patient usually experiences complete recovery.

THE IRON LUNG

People with polio often lose the ability to move their legs and/or arms. This disability is a terrible disaster. But it does not necessarily cause death. If polio also causes loss of control over the respiratory muscles, however, death can and often does occur. For polio patients, then, a device to help them breathe is an absolute necessity.

In 1982, the American physiologist Philip Drinker (1893–1977) invented the most famous of all devices for helping polio patients to breathe. The device was called the Drinker tank respirator. It is more commonly known as an iron lung.

The iron lung is an airtight cylindrical steel drum. It encloses the entire body with only the patient's head exposed. Pumps connected to the device lower and raise air pressure within the drum. As the drum contracts and expands, it forces the patient's chest to contract and expand also. The iron lung forces the patient's body to continue breathing.

Many polio patients were kept alive by the iron lung. They had to spend many years enclosed in the lung, with only short periods outside it. With the development of the Salk and Sabin vaccines, polio has nearly become extinct. As a result, the iron lung no longer finds much use in today's hospitals.

About 1 percent of people infected with the poliovirus develop the most serious symptoms of the disease. At first, they experience only mild symptoms. After a few days, however, the symptoms become much worse. They include severe headache and neck and back pain.

The worst effects of polio are caused when the virus invades motor nerves. Motor nerves are nerves that control the movement of muscles. The virus can destroy these nerves. As the nerves die, muscles lose their ability to move. They first become floppy and weak. Eventually they become paralyzed and lose the ability to move at all. After a few days, the muscles actually begin to decrease in size. The person does not lose the sense of touch in the affected areas, however.

The virus can also infect the brain stem. The brain stem is located at the base of the brain. It connects the brain to the spinal cord. A person may have trouble breathing and swallowing. In the severest cases, the heart rate and blood pressure may be disturbed. These changes can lead to the patient's death.

The maximum degree of paralysis usually occurs within a few days. After that time, some healthy nerves may try to take the place of the damaged nerves. This process lasts about six months. After that time, no further improvement is likely.

DIAGNOSIS

Polio is now a rare disease in the United States. Many doctors have never seen a case of polio. A few symptoms are quite distinctive, however. A fever and paralysis without the loss of feeling is one clue to the presence of polio.

If a doctor suspects polio, the usual follow-up test is a lumbar puncture, or "spinal tap." A lumbar puncture is a procedure in which a sample of spinal fluid is removed with a long, thin needle. The spinal fluid can be examined for an elevated level of white blood cells and the absence of bacteria. These two factors taken together are a strong indication of polio.

The spinal fluid can also be tested for the presence of polio antibodies. Antibodies are chemicals produced by the immune system to fight against specific foreign invaders, such as the poliovirus.

TREATMENT

There is no cure for polio. Patients can be treated to make them more comfortable, however. For example, medications can reduce pain. Hot packs help soothe sore muscles. Artificial ventilation (breathing machines) may be necessary if a person's respiratory system is affected. Walking aids, such as crutches and walkers, may be necessary for someone whose leg muscles are damaged by the disease.

PROGNOSIS

The prognosis for mild and moderate polio is good. Most patients recover completely within a short period of time. Of those who have the severest form of polio, about half will recover completely. A quarter will experience some disability, and another quarter will have permanent and serious disability. About 1 percent of all those who have the most serious form of polio die of the disease.

In recent years, a new medical problem known as postpolio syndrome has been diagnosed. The condition shows up thirty years or more after a person has had a mild or moderate form of the disease. Postpolio syndrome affects about 25 percent of polio patients. The major symptom of postpolio syndrome is a very slow decrease in muscle strength.

PREVENTION

Polio can now be prevented by immunizations. An immunization is an injection that protects a person against some type of infectious disease. Two kinds of polio immunizations are available in the United States. The Salk vaccine contains dead polioviruses. It is injected just under the skin. The dead viruses cause the immune system to start making antibodies against the poliovirus. If a person is infected with the poliovirus later in life, the immune system can protect the body against the disease.

The Sabin vaccine contains polioviruses that are very weak but not dead. They produce the same effect on the immune system as dead viruses. Both vaccines are highly effective in preventing polio. In fact, some public-health experts think the disease may be completely wiped out in the next decade.

FOR MORE INFORMATION

Books

Daniel, Thomas M., and Frederick C. Robbins, eds. Polio. Rochester: University of Rochester Press, 1997.

Gould, Tony. A Summer Plague: Polio and Its Survivors. New Haven, CT: Yale University Press, 1997.

Halstead, Lauro S., ed. Managing Post Polio: A Guide to Living Well with Post Polio. Arlington, VA: ABI Professional Publications, 1998.

Weaver, Lydia. Close to Home: A Story of the Polio Epidemic. New York: Puffin, 1997.

Organizations

International Polio Network. 4207 Lindell Blvd., Suite 110, St. Louis, MO 63108–2915. (314) 534–0475.

March of Dimes Birth Defects Foundation. National Office. 1275 Mamaroneck Ave., White Plains, NY 10605. http://www.modimes.org.

Polio Survivors Association. 12720 Lareina Ave., Downey, CA 90242. (310) 862–4508.

Web sites

"Ask NOAH About: Neurological Problems." NOAH: New York Online Access to Health. [Online] http://www.noah.cuny.edu/neuro/neuropg.html# POLIO AND POST-POLIO SYNDROME (accessed on October 28, 1999).

Polio.com. [Online] http://www.polio.com (accessed on October 28, 1999).

"Polio/Post-Polio Information Directory." Polio Society Home Page. http://www.polio.org (accessed on October 28, 1999).

POLIO

Fear of Polio

During the early 1950s no disease attracted as much attention as polio. A Gallup poll conducted in 1954 when the Salk vaccine was being tested indicated that more people knew about the polio vaccine tests than knew the name of the president. Polio struck children far more often than adults, and there seemed to be little a parent could do to protect against it. Moreover, it struck without regard to the victim's race or social class, and so it demanded the attention of both the medical and political establishments. When Dr. Hart E, Van Riper, the director of the NFIP, announced in 1953 that more cases of polio had been reported in the past five years than in the previous twenty, many parents failed to hear that he was optimistic about a cure.

Polio Warnings

The rumor mill was pernicious as ever. Dr. Van Riper dispelled the notion that fruit, insects, animals, and bad genes cause polio. As polio tended to strike during the summer, he advised parents that they could send their children to camp if the camp had proper medical supervision, but he warned against camps where polio had been reported. He cautioned parents about letting their children mix with crowds or come into close contact with stangers in such settings as movie theaters, playgrounds, or beaches. He advised that swimming pools do not themselves cause polio, but crowds at swimming pools might increase the risk of transmission, and the fatigue of a hard day at play as well as the chill of getting out of the water might increase a child's susceptibility.

Polio Precautions

As a result of the information distributed by the NFIP, public swimming pools were closed. Children were confined to their yards during the summer, especially in warmer climates, where the virus seemed to thrive. Active boys and girls were encouraged to play quietly because sweating was thought to promote polio. Children were discouraged from playing with any but their closest friends.

How Polio Spreads

Polio is an infectious disease. It is caused by any one of three types of virus that enters the body through a patient's mouth and resides briefly in the bloodstream before taking one of two routes. The virus may make its way into the bowels, where it is expelled without more serious harm to the patient than the symptoms of a common cold. If the patient is unlucky, the virus travels into the central nervous system instead, where it irreparably damages cells in the brain stem or spinal cord and can cause severe paralysis and, sometimes, death.

Effects of Polio

According to Dr. Van Riper, about 50 percent of all polio victims recovered completely, some 30 percent suffered mild aftereffects, about 14 percent suffered severe paralysis, and about 6 percent died. These latter two categories comprise what are called acute cases, of which 28,386 were reported in 1950. In 1952 the number of acute cases had risen to 55,000.

History

Polio is thought to have existed since ancient times, and it was known to be caused by a virus since 1908. It did not become a public health threat, though, until the twentieth century, when in 1916 about twenty-seven thousand acute cases were reported in the northeast and north-central states. In 1921 it struck Franklin D. Roosevelt, who was elected president of the United States eleven years later. He founded the NFIP in 1938, a charity supported by an annual national fund-raising effort called the March of Dimes.

Early Vaccines

In 1950 the medical community responded to the rising public fear of polio with a safeguard of dubious value. Researchers discovered that injections of gamma globulin, a part of human blood that carries antibodies against infectious viruses, could temporarily prevent polio infection. The problem was that immunity lasted for only one to eight days, and gamma globulin was in short supply, because it was used in the vaccine against measles that was routinely administered to school-age children. People wanted better protection for their children.

POLIO MASQUERADES

In 1953 Dr. Max J. Fox and Irvin Moskowitz reported in the Wisconsin Medical Journal that as many as one-third of the patients admitted to hospital for treatment as polio victims only feared they had the disease. These so called hysterical paralytics typically exhibited a morbid interest in poliomyelitis and suffered the symptoms of the disease without any physical cause. Sypmtoms usually disappeared when the patient was assured that he or she was disease-free. Often psychological care was recommended.

Even when there were clearly physical causes of polio-like symptoms, diagnosis was uncertain in the early 1950s. The Southwestern Poliomyelitis Center in Houston reported that about one in six patients diagnosed as having polio suffered instead from another, less serious disease. The reason was that doctors, who were taught in medical school that it is better to be safe than sorry in diagnoses, were reluctant to rule out polio in patients who exhibited any of the symptoms of the disease.

Jonas Salk

(See Salk entry) A more encouraging alternative was offered by reports in the early 1950s of the research being directed by Dr. Jonas Salk, a young doctor at the University of Pittsburgh. He had developed a vaccine consisting of all three types of polio viruses, killed by dipping them in formaldehyde. The vaccine was injected into the bloodstream, where it caused the body to develop protective antibodies. The Salk vaccine was administered in three shots to the arm, 1 cc of pink liquid each. The second shot came two weeks after the first, and the third one month later.

Polio Pioneers

In the spring of 1954 the Salk vaccine was tested on 1.8 million schoolchildren, called Polio Pioneers. Of these, 440,000 children got the Salk vaccine; 210,000 got what were called dummy shots, or placebos; the rest were simply observed as a control group. The test results, announced in April 1955, showed that those who received the placebo contracted 3.5 times more cases of polio than those children who received the vaccine. The Salk vaccine was proven, and President Eisenhower encouraged passage of the Poliomyelitis Vaccination Act, which provided $30 million to states to buy the vaccine for the general population, children first. A consortium of four major drug companies mobilized to provide 9.8 million doses for elementary-school children in 1955. The vaccine, which cost the government about a dollar for each three-shot sequence, was administered free in the summer of 1955, first to every first grader, then to children in grades two to four, then to pregnant women past the twelfth week of pregnancy. Children got their shots at schools and other public places. By the end of 1958, 200 million shots of Salk vaccine were given.

Drawbacks to Salk Vaccine

The benefits of the Salk vaccine had limitations: it conferred polio immunity for only about thirty months, at which time a booster shot was required. It also turned out that the vaccine was difficult to mass-produce. The polio viruses were hard to kill in large quantities, and if live viruses made it into the vaccine, the serum could cause the disease it promised to prevent, as it did in 1955 when Cutter Laboratories of Berkeley, California, delivered a batch of partially live vaccine that infected forty-four children with polio within days of vaccination. Salk provided an admirable stopgap antidote to the polio epidemic, but the search continued for a better solution to the problem.

Types of Vaccines

In general, vaccines come in two types. The first consists of dead viruses, like the Salk vaccine, that cause the body to produce antibodies that will, for a short time, disable any live virus introduced into the bloodstream. The second consists of attenuated, or weakened, live viruses that are too impotent to cause the disease but strong enough to stimulate the body to produce more antibodies for a longer time. Live-virus vaccines confer a lengthier period of immunity and an increased likelihood that the virus type, which cannot reproduce itself outside the body, will be eradicated altogether.

Albert Sabin

(See Sabin entry.) The leader in the attempt to produce a live-virus vaccine was Albert Sabin, who successfully tested his vaccine on thirty prisoner-volunteers in 1955. His announcement on 6 October 1956 that his vaccine was ready for mass testing created only an anxious stir in America, where the principle that the only good virus is a dead virus held sway. In a gesture characteristic of the cold war, the Polish-born Sabin was allowed to accept the invitation of Soviet scientists to test his vaccine there. Only after he had successfully vaccinated millions of Soviet schoolchildren did Americans adopt his vaccine in 1961. Children were delighted, because they no longer had to take polio shots. The Sabin vaccine was administered by mouth in a 2-cc, cherry-flavored dose.

Sabin's Effects

The names Salk and Sabin have come to represent the fight against polio, but thousands of researchers devoted their talents to the search for a polio shield in the 1950s, and Americans donated hundreds of millions of dollars for polio research and patient care to the March of Dimes. As people expected, the fight was won. The incidence rate of polio fell from 37.2 cases per 100,000 Americans in 1952 to 1.8 cases per 100,000 in 1960. By the 1980s fewer than ten cases were reported each year. (See Koporowski entry).

Sources:

Alton L. Blakeslee, Polio and the Salk Vaccine: What You Should Know Aboutit (New York: Grosset OcDunlap, 1956);

Richard Carter, Breakthrough: The Saga of Jonas Salk (New York: Pocket Books, 1967);

"O Pioneers!" New Yorker, 30 (8 May 1954): 24-25;

"Polio: Free Shots" Newsweek, 4 (1 November 1954): 62-63.

Polio

Definition

Poliomyelitis, also called polio or infantile paralysis, is a highly infectious viral disease that may attack the central nervous system and is characterized by symptoms that range from a mild nonparalytic infection to total paralysis in a matter of hours.

Description

There are three known types of polioviruses (called 1, 2, and 3), each causing a different strain of the disease and all being members of the viral family of enteroviruses (viruses that infect the gastrointestinal tract). Type 1 is the cause of epidemics, and many cases of paralysis, which is the most severe manifestation of the infection. The virus is usually a harmless parasite of human beings. Some statistics quote one in 200 infections as leading to paralysis, while others state that one in 1,000 cases reach the central nervous system (CNS). When it does reach the CNS, inflammation and destruction of the spinal cord motor cells (anterior horn cells) occurs, which prevents them from sending out impulses to muscles. This causes the muscles to become limp or soft, and they cannot contract, a condition called flaccid paralysis and is the type found in polio. The extent of the paralysis depends on where the virus strikes and the number of cells that it destroys. Usually, some of the limb muscles are paralyzed; the abdominal muscles or muscles of the back may be paralyzed, affecting posture. The neck muscles may become too weak for the head to be lifted. Paralysis of the face muscles may cause the mouth to twist or the eyelids to droop. Life may be threatened if paralysis of the throat or of the breathing muscles occurs.

Humans are the only natural host for polioviruses, and it most commonly infects younger children, although older children and adults can be infected. Crowded living conditions and poor hygiene encourage the spread of poliovirus. Risk factors for this paralytic illness include older age, pregnancy, abnormalities of the immune system, and a recent episode of excessively strenuous exercise concurrent with the onset of the CNS phase. As of 2004, the last naturally occurring polio case in the United States was diagnosed in 1979.

Causes and symptoms

Poliovirus can be spread by direct exposure to an infected individual, and more rarely, by eating foods contaminated with waste products from the intestines (feces) and/or droplets of moisture (saliva) from an infected person. Thus, the major route of transmission is fecal-oral, which occurs primarily with poor sanitary conditions. The virus is believed to enter the body through the mouth with primary multiplication occurring in the lymphoid tissues in the throat, where it can persist for about one week. During this time, it is absorbed into the blood and lymphatics from the gastrointestinal tract where it can reside and multiply, sometimes for as long as 17 weeks. Once absorbed, it is widely distributed throughout the body until it ultimately reaches the CNS (the brain and spinal cord). The infection is passed on to others when poor hand washing allows the virus to remain on the hands after eating or using the bathroom. Transmission remains possible while the virus is being excreted and it can be transmitted for as long as the virus remains in the throat or feces. The incubation period ranges from three to 21 days, but cases are most infectious from seven to ten days before and after the onset of symptoms.

There are two basic patterns to the virus: the minor illness (abortive type) and the major illness (which may be paralytic or nonparalytic). The minor illness accounts for 80 to 90 percent of clinical infections and is found mostly in young children. It is mild and does not involve the CNS. Symptoms include a slight fever , fatigue, headache , sore throat , and vomiting , which generally develop three to five days after exposure. Recovery from the minor illness occurs within 24 to 72 hours. Symptoms of the major illness usually appear without a previous minor illness and generally affect older children and adults.

About 10 percent of people infected with poliovirus develop severe headache and pain and stiffness of the neck and back. This is due to an inflammation of the meninges (tissues which cover the spinal cord and brain). This syndrome is called aseptic meningitis . The term aseptic is used to differentiate this type of meningitis from those caused by bacteria. The patient usually recovers completely from this illness within several days.

About 1 percent of people infected with poliovirus develop the most severe form. Some of these patients may have two to three symptom-free days between the minor illness and the major illness, but the symptoms often appear without any previous minor illness. Symptoms again include headache and back and neck pain. The major symptoms, however, are due to invasion of the motor nerves, which are responsible for movement of the muscles. This viral invasion causes inflammation and then destruction of these nerves. The muscles, therefore, no longer receive any messages from the brain or spinal cord. The muscles become weak, floppy, and then totally paralyzed. All muscle tone is lost in the affected limb and the muscle becomes soft (flaccid). Within a few days, the muscle begins to decrease in size (atrophy). The affected muscles may be on both sides of the body (symmetric paralysis) but are often on unbalanced parts of the body (asymmetric paralysis). Sensation or the ability to feel is not affected in these paralyzed limbs.

When poliovirus invades the brainstem (the stalk of brain which connects the two cerebral hemispheres with the spinal cord, called bulbar polio), a person may begin to have trouble breathing and swallowing. If the brainstem is severely affected, the brain's control of such vital functions as heart rate and blood pressure may be disturbed, a condition that can lead to death.

The maximum state of paralysis is usually reached within just a few days. The remaining, unaffected nerves then begin the process of attempting to grow branches, which can compensate for the destroyed nerves. Fortunately, the nerve cells are not always completely destroyed. By the end of a month, the nerve impulses start to return to the apparently paralyzed muscle and by the end of six months, recovery is almost complete. If the nerve cells are completely destroyed; however, paralysis is permanent.

Diagnosis

Fever and asymmetric flaccid paralysis without sensory loss in a child or young adult almost always indicate poliomyelitis. Using a long, thin needle inserted into the lower back to withdraw spinal fluid (lumbar puncture) will reveal increased white blood cells and no bacteria (aseptic meningitis). Nonparalytic poliomyelitis cannot be distinguished clinically from aseptic meningitis due to other agents. Virus isolated from a throat swab and/or feces or blood tests demonstrating the rise in a specific antibody is required to confirm the diagnosis.

Treatment

There is no specific treatment for polio except symptomatic. Therapy is designed to make the patient more comfortable (pain medications and hot packs to soothe the muscles), and intervention if the muscles responsible for breathing fail (for instance, a ventilator to take over the work of breathing). During active infection, rest on a firm bed is indicated. Physical therapy is the most important part of management of paralytic polio during recovery.

Prognosis

When poliovirus causes only the minor illness or simple aseptic meningitis, the patient can be expected to recover completely. Among patients with the major illness, about 50 percent recover completely. About 25 percent of such patients have slight disability, and about 25 percent have permanent and serious disability. Approximately 1 percent of all patients with major illness die. The greatest return of muscle function occurs in the first six months, but improvements may continue for two years.

Post-polio syndrome (PPS) is a condition that can strike polio survivors anywhere from 10 to 40 years after their recovery from polio. It is caused by the death of individual nerve terminals in the motor units that remain after the initial polio attack. Symptoms include fatigue, slowly progressive muscle weakness, muscle and joint pain, and muscular atrophy. The severity of PPS depends upon how seriously the survivors were affected by the first polio attack.

Prevention

There are two types of polio immunizations available in the United States, but since the year 2000, one is rarely used. A vaccine takes advantage of the fact that infection with polio leads to an immune reaction, which will give the person permanent, lifelong immunity from reinfection with the form of poliovirus for which the person was vaccinated.

The Salk vaccine (also called the killed polio vaccine or inactivated polio vaccine, IPV) consists of a series of three shots that are given just under the skin to children at the ages of two months, four months, and any time between six and 18 months. A fourth injection is given between the ages of four to six years as a booster. This immunization contains no live virus, just the components of the virus that provoke the recipient's immune system to react as if the recipient were actually infected with the poliovirus. The recipient thus becomes immune to infection with the poliovirus.

KEY TERMS

Aseptic —Sterile; containing no microorganisms, especially no bacteria.

Asymmetric —Not occurring equally on both sides of the body.

Atrophy —The progressive wasting and loss of function of any part of the body.

Brainstem —The stalk of the brain which connects the two cerebral hemispheres with the spinal cord. It is involved in controlling vital functions, movement, sensation, and nerves supplying the head and neck.

Epidemic —Refers to a situation in which a particular disease rapidly spreads among many people in the same geographical region in a relatively short period of time.

Flaccid —Flabby, limp, weak, or floppy.

Gastrointestinal —Pertaining to the digestive organs and structures, including the stomach and intestines.

Lymph —Clear, slightly yellow fluid carried by a network of thin tubes to every part of the body. Cells that fight infection are carried in the lymph.

Paralysis —Loss of the ability to move one or more parts of the body voluntarily due to muscle or nerve damage.

Symmetric —Occurring on both sides of the body, in a mirror-image fashion.

Since the year 2000, the Sabin vaccine (also called the oral polio vaccine or OPV) has been discontinued in the United States, although it is still being used in other countries. It contains the live, but weakened, poliovirus and because OPV uses the live virus, it has the potential to cause infection in individuals with weak immune defenses (both in the person who receives the vaccine and in close contacts). Approximately nine cases a year of vaccine related polio was associated with OPV in the United States. Although this is a rare complication, occurring in only one in 6.8 million doses administered and one in every 6.4 million doses from having close contact with someone who received the vaccine, the risk of having polio from OPV was greater than it was of naturally acquiring it.

Following the launching of the Global Polio Eradication Initiative, the number of cases fell 99 percent from an estimated 350,000 cases to less than 3,500 cases worldwide in 2000. At the end of 2000, the number of polio-infected countries was approximately 20, down from 125. The goal of the World Health Organization (WHO) is to have polio eliminated from the planet by the year 2005. The virus has still been identified in Africa and parts of Asia, so travelers to those areas may want to check with their physicians concerning booster vaccinations.

Resources

BOOKS

Oshinsky, David. Polio: An American Story. Oxford, UK: Oxford University Press, 2004.

PERIODICALS

Alexander, L. N., et al. "Vaccine Policy Changes and Epidemiology of Poliomyelitis in the United States" Journal of the American Medical Association 292 (2004): 1696–1701.

ORGANIZATION

International Polio Network. 4207 Lindell Blvd., Suite 110, St. Louis, MO 63108–2915. Web site: <www.postpolio.org>.

March of Dimes Birth Defects Foundation. National Office, 1275 Mamaroneck Avenue, White Plains, NY 10605. Web site: <www.modimes.org/>.

WEB SITES

World Health Organization. Global Polio Eradication Progress 2004. Available online at <www.polioeradication.org/>.

Linda K. Bennington, MSN,CNS