Polio is a very dangerous disease caused by a virus that attacks the intestinal tract and in a few cases travels to the spinal cord to damage the nerves. Children and adults who get a serious case of polio become paralyzed. They may be crippled or even die from the disease. Mild cases of polio may last only a few days and may cause the person to have a fever, sore throat, stomach ache, and headache.
Polio occurs most often in summer and fall and generally attacks children under 5 years of age. In 1995, it was claimed that 100,000 children a year are crippled by it. Previously, the World Health Organization estimated that 220,000 children were paralysed and 23,000 killed by polio every year in developing countries.
Since the widespread introduction of vaccination against poliomyelitis, around 1957, the incidence of this disease has fallen to insignificant proportions in North America, parts of Europe, and several countries in other parts of the world; in 1968 there were only 24 cases in England and Wales, compared with 3,200 in 1956. In Sweden and Finland, paralytic poliomyelitis has disappeared following immunization programmes with multiple doses of inactivated vaccine that covered close to 100% of the population. Polio can however return to countries from which it was previously eradicated, as happened in 1992 in a Dutch religious community opposed to immunization.
Although there have been no recent cases of polio reported in the Western Hemisphere, there are still thousands of polio cases each year in many developing countries in Africa, Asia, the Middle East, and Eastern Europe. India has 60% of the world's polio cases. In 1996, 155 countries reported no cases of polio, 18 countries had one case, and 27 countries reported more than 10 cases. 14 countries did not submit reports.
In large areas of Africa, Asia and Latin America the incidence appears to have been rising disconcertingly during recent years, and large outbreaks are being reported there with increasing frequency. In many tropical countries paralytic poliomyelitis is a far more common disease than has been appreciated.