Polio, or poliomyelitis, is a serious infectious disease caused by a virus that affects the central nervous system. Polio, sometimes called infantile paralysis, primarily affects children. When the virus first takes hold, symptoms begin with body aches and a stiff neck. As the disease progresses, itaffects nerve tissue causing paralysis and the wasting of muscle tissue. Before inoculation was available, polio was a dread disease that killed many, because paralysis of the breathing muscles caused suffocation. Today, due to immunization programs and the World Health Organization's Global Technical Consultative Group on Polio Eradication program, a total of only 4,116 polio cases were reported worldwide in 1997, a decline of 90 percent worldwide since the program began in the late 1980s. With the disease still widely foundin Bangladesh, India, Nepal, Pakistan, South Asia, the Congo, Nigeria, West and Central Africa, Ethiopia, Somalia, Sudan, and the Horn of Africa, WHO is in the final stage of their push for the total eradication of polio.

There is evidence to suggest that polio was known more than 3,000 years ago in Egypt and continued to paralyze people well into this century. In the earlypart of the twentieth century in America, there were numerous outbreaks of the disease including the 1916 epidemic in which 27,000 people developed polio, almost 7,000 of whom died and many thousands more who were left paralyzed.The only treatment was physical therapy to ease the paralysis.

In 1929 a young man was the first polio patient to be aided by a new kind oftherapy--the Drinker tank respirator, or iron lung, invented by Philip Drinker, a professor at the School of Public Health at Harvard University. Drinkerplaced his patient into an airtight metal box from the neck down. The patient's mouth and nose remained outside the box, which was connected to a pump which reduced air pressure inside the box, imitating the negative change in pressure in the chest cavity that occurs during an inhalation. The decreased airpressure inside the box drew air through the nose and mouth of the patient into the lungs. Use of the iron lung ushered in an era in which many polio patients could be kept alive. Still, there was no cure, and little was known of its causative agent.

An Austrian-American physician, Karl Landsteiner (who won a 1930 Nobel prizefor discovering human blood groups) was the first to postulate that polio wascaused by a virus. Between 1908 and 1919, while working at the Royal-Imperial Hospital in Vienna, he examined many patients who had died of polio. In experiments, he took spinal cord and brain tissue from a polio victim and injected it into monkeys. The animals developed polio symptoms, and when Landsteiner was unable to detect any bacteria, he believed the cause to be a virus.

After the discovery of the causative virus, the success of eradicating the disease is credited primarily to the work of two men, Jonas Salk and Albert Sabin. Salk began his immunology research in 1938 at New York University and participated in a program to identify the known strains of the polio virus at the University of Pittsburgh. His research was aided by the earlier work of Nobel Prize winners John Enders, Frederick C. Robbins, and Thomas Weller, who had perfected techniques of growing large quantities of polio virus on monkey kidney tissue. Salk grew the viruses and then killed them with formaldehyde. This killed-virus mixture proved to be an effective vaccine which was tested nationally starting in 1954. It is estimated that Salk's vaccine proved 60-90%effective against the disease.

During the time Salk was testing his vaccine, Sabin was developing a live-virus vaccine grown on monkey kidney tissue. In 1959, the Polish-American physician began testing his vaccine on millions of Russians. His vaccine proved more effective than Salk's and had two advantages: the live-virus vaccine conferred longer-lasting immunity, and could also be administered orally. After Great Britain began using the Sabin oral vaccine in 1962, the United States followed suite, and it is still the standard immunization practice today.

Although polio itself is almost conquered, many people who contracted the disease as long ago as thirty years are experiencing what some researchers believe to be "post-polio syndrome," or PPS, which manifests as fatigue, pain, andmuscle weakness. Some investigators have discovered viral fragments in the spinal fluid of PPS patients which closely resemble the poliovirus, indicatingit may persist in the central nervous system in a mutated, nonvirulent, andnonreplicating form, prompting, however, immune system response.

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