Poliomyelitis

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POLIOMYELITIS

POLIOMYELITIS, or infantile paralysis, was one of the most feared diseases of the twentieth century, especially for its ability to cripple children and adolescents. The disease is caused by one of three strains of intestinal virus that under certain conditions invades and damages or destroys the anterior horn cells of the spinal cord. Paralysis is caused when damaged or destroyed nerves can no longer enervate muscles. The virus is commonly spread through contaminated fecal material. Before modern sanitation the poliovirus was constantly present, and most individuals were infected as young children, thereby gaining protective antibodies. Epidemics occurred when modern sanitation interrupted virus circulation for several years, creating a large susceptible population. In epidemics, perhaps as many as 90 to 95 percent of those infected had inapparent cases and a flu-like illness with no paralysis. Four to eight percent of those infected had an abortive case with mild symptoms. Less than 2 percent of all infections reached the central nervous system and caused paralysis. Polio killed when the muscles involved in breathing were paralyzed, but the disease was rarely fatal.

The first sizable polio epidemic in the United States occurred in Vermont in 1894. Recurrent epidemics in Europe and North America sparked research on the disease, and in 1908 the Vienna immunologist Karl Landsteiner discovered the poliovirus. Simon Flexner, the director of the Rockefeller Institute for Medical Research in New York, soon isolated the virus in the United States and discovered polio antibodies in patients.

In 1916, New York and the Northeast experienced the nation's most severe polio epidemic, with 27,000 cases and 6,000 deaths. In New York City alone there were 8,928 cases and 2,407 deaths. This epidemic puzzled physicians and frightened citizens. Polio struck both infants and adults, individuals living in clean, sanitary conditions and those living in filth, the wealthy and the poor. Lacking effective cures and vaccines, public health officials conducted a campaign to clean up the city and eradicate the flies believed to carry the disease. Polio patients were quarantined in their homes or removed, sometimes forcibly, to hastily established isolation hospitals. For the next four decades epidemics of poliomyelitis struck some part of the nation every year.

In 1921, Franklin D. Roosevelt, who later served as governor of New York and president of the United States, developed polio while vacationing at the family home. Seeking to regain the use of his paralyzed legs, he discovered the therapeutic effects of warm mineral water at a failing resort in Warm Springs, Georgia. In 1926 he purchased the resort and, with the help of his law partner, Basil O'Connor, turned it into a model facility for polio rehabilitation, although Roosevelt himself never walked unaided.

During the 1920s and 1930s, scientists and physicians sought to better understand the disease and to find a cure or vaccine. The researchers James D. Trask, John R. Paul, and Dorothy Horstmann of the Yale University Poliomyelitis Study Unit confirmed polio's character as an intestinal disease when they isolated the virus in water supplies and sewage during epidemics. Australian scientists in 1931 discovered that there were at least two different strains of poliovirus. Scientists ultimately discovered a third strain and placed the poliovirus in the family of enteroviruses. In 1935 two American physicians, Maurice Brodie in New York and John A. Kolmer in Philadelphia, developed and tested polio vaccines. These vaccines, however, proved ineffective and may actually have caused cases of the disease.

Polio rehabilitation also advanced in the 1930s, especially at the Georgia Warm Springs Foundation established by Roosevelt. The President's Birthday Ball Commission began raising funds in 1934 to support rehabilitation and research and was succeeded in 1938 by the National Foundation for Infantile Paralysis headed by Basil O'Connor. The National Foundation's March of Dimes campaign raised over $600 million between 1938 and 1962. About 60 percent of this money assisted individuals with hospital and doctor bills, and about 11 percent was spent on grants to scientists. The iron lung, a large canister-shaped respirator that "breathed" for patients with paralyzed respiratory muscles was developed in the 1930s. In the 1940s, Elizabeth Kenny, an Australian nurse, introduced her unorthodox ideas for treating polio paralysis. In place of immobility and casts to prevent the contraction of paralyzed limbs, Kenny applied hot packs to sooth paralyzed muscles and movement in order to maintain flexibility and retrain paralyzed muscles. Although many doctors rejected her theories about the causes of polio paralysis, her therapeutic practices soon became commonplace.

In the late 1940s, John F. Enders, Thomas H. Weller, and Frederick C. Robbins, physicians at Harvard funded by the National Foundation, first grew poliovirus on tissue culture outside the body, necessary for a successful vaccine. They won the Nobel Prize in 1954 for their discovery. The National Foundation also funded a typing program to identify all the possible strains of the virus in anticipation of producing a vaccine against every variant.

This research occurred against the background of an increasing incidence of epidemics in the late 1940s and early 1950s. Nine of the ten worst years for polio occurred between 1945 and 1955, and the epidemic of 1952 was second only to 1916 in its severity. The improved sanitation of the postwar years, the move to the suburbs, and the baby boom ensured that many children and even adolescents were vulnerable. Those years were marked by summers of fear when parents kept their children out of swimming pools and movie theaters and warned them against drinking from water fountains. The fund-raising of the March of Dimes, the information disseminated by the National Foundation, and the heartbreaking personal narratives that appeared in popular magazines kept polio in the forefront of the nation's consciousness. The specter of the crippling paralysis of polio threatened the postwar American Dream of healthy, happy children.

The fund-raising efforts of the March of Dimes and the laboratory work of the physicians came together in the 1950s. Jonas Salk, a University of Pittsburgh physician, applied lessons he had learned working on influenza vaccine and developed a successful killed virus vaccine that could be mass produced. By the early 1950s he was conducting preliminary trials of the vaccine. In 1954 the National Foundation arranged for a large-scale field trial of the Salk vaccine conducted by Dr. Thomas Francis Jr. of the University of Michigan. Over 1.8 million children were enrolled as "polio pioneers" in the trial. On 12 April 1955, Francis announced that the Salk vaccine was both safe and effective in protecting vaccinated children from polio. The U.S. government licensed the vaccine the same day. Basil O'Connor had already ordered millions of doses from pharmaceutical companies in order to begin a mass vaccination immediately. Unfortunately, a few weeks later, a bad batch of vaccine produced by Cutter Laboratories resulted in more than 200 cases of vaccine-associated poliomyelitis, including eleven deaths. This was an isolated episode, and the vaccination of America's children soon continued. Even as many children were protected by the Salk vaccine, Albert Sabin, also supported by the National Foundation, worked on an attenuated poliovirus vaccine. An attenuated vaccine, in which the virus was live but significantly weakened, had several advantages. It induced a stronger, longer lasting immune response; immunity was achieved more quickly; and it could be given orally instead of being injected. After field trials in the United States, the Soviet Union, and elsewhere, the Sabin vaccine was licensed for use in 1962. These two vaccines virtually eliminated poliomyelitis in the United States by the early 1960s. Since then only a handful of cases have occurred annually, usually in new immigrants or as vaccine-associated cases.

The survivors of the postwar polio epidemics often spent long periods in rehabilitation hospitals before being fitted with braces, wheelchairs, and respirators that allowed them to return to families, school, and work. Because of the barriers they faced in attempting to live and work, polio survivors were often in the forefront of the disability rights movement that emerged in the 1970s. Activists like Ed Roberts, who was one of the founders of the Independent Living Movement, insisted that individuals with disabilities had a right to accessible living and working environments. In the 1980s, many polio survivors began experiencing increased pain, muscle weakness and even paralysis that physicians eventually identified as post-polio syndrome, an apparent effect of the overuse of nerves and muscles to compensate for the destruction caused by the initial infection. The oral polio vaccine also came under attack in the United States for causing eight to ten cases of polio every year. In 2000 the federal government recommended returning to a safer Salk-type killed virus. The Sabin vaccine, however, remained in use overseas as the World Health Organization tried to eradicate the poliovirus worldwide. Thus in the twenty-first century, poliomyelitis, which was so feared in the twentieth century, may become only the second infectious disease, after smallpox, to be eliminated as a threat to humans.