Information on Poliomyelitis

What is Polio?
Poliomyelitis (polio) is a highly infectious disease caused by a virus. It invades the nervous system, and can cause total paralysis in a matter of hours. The virus enters the body through the mouth and multiplies in the intestine.

What are the symptoms of polio?
Initial symptoms are fever, fatigue, headache, vomiting, stiffness in the neck and pain in the limbs. One in 200 infections leads to irreversible paralysis (usually in the legs). Amongst those paralyzed, 5%-10% die when their breathing muscles become immobilized. Although polio paralysis is the most visible sign of polio infection, fewer than 1% of polio infections ever result in paralysis.

Who is most at risk of polio?
Polio can strike at any age, but affects mainly children under three (over 50% of all cases). However, immune and or partially immune adults and children can still be infected with poliovirus and carry the virus for long enough to take the virus from one country to another, infecting close contacts and contaminating sanitation systems. This could facilitate transmission especially in countries where sanitation systems are sub-standard.

How is polio spread?
Poliovirus is mainly passed through person-to-person contact. The virus enters the environment through feces of people infected then is passed to others especially in situations of poor hygiene. The poliovirus can also infect persons who have been vaccinated and can be carried by them. Such individuals will not develop polio, but can carry the virus in their intestines and can pass it to others in conditions of sub-standard hygiene. Poliovirus can spread widely before cases of paralysis are seen. As most people infected with poliovirus have no signs of illness, they are never aware they have been infected. After initial infection with poliovirus, the virus is shed intermittently in feces (excrement) for several weeks. During that time, polio can spread rapidly through the community.

How prevalent is polio?
Until the 1950s, polio crippled thousands of children every year in industrialized countries. Soon after the introduction of effective vaccines, polio was brought under control, and practically eliminated as a public health problem in industrialized countries.

It took somewhat longer for polio to be recognized as a major problem in developing countries. Today, the disease has been eliminated from most of the world, and only seven countries worldwide remain polio-endemic. This represents the lowest number of countries with circulating wild poliovirus. At the same time, the areas of transmission are more concentrated than ever - 98 percent of all global cases are found in India, Nigeria and Pakistan.

How can polio be prevented?
There is no cure for polio, it can only be prevented through immunization. Polio vaccine, given multiple times, almost always protects a child for life. Full immunization will markedly reduce an individual's risk of developing paralytic polio. Full immunization will protect most people, however individuals can still contract the disease due to the failure of some individuals to respond to the vaccine.

Source: Global Polio Eradication Initiative (http://www.polioeradication.org/), July 6, 2006.