Polio Poliomyelitis

Polio (poliomyelitis) is an acute highly infectious viral disease which mainly affects young children. It is caused by three types of poliovirus, Types 1, 2, and 3. Poliovirus infection occurs in the gastrointestinal tract and spreads in a minority of cases to the nervous system.

Polio cases have decreased worldwide by over 99 percent since 1988 due to a global effort to eradicate the disease. In countries that report polio cases, roughly 70-80 percent of cases are less than 3 years of age and 80-90 percent of cases are less than 5 years of age.

Susceptibility to infection is universal, however, paralysis occurs in only about 1 percent of infections. Paralysis occurs more frequently in infected, non-immune adults than in non-immunised infants and young children. Type-specific immunity lasts for the patients’ entire lives. Second attacks are rare and result from infection with poliovirus of a different type.

Many polio infections show no symptoms at all. When present, initial symptoms of polio include fever, fatigue, headache, vomiting, stiffness in the neck, and pain in the limbs. A small proportion of infections (one in 200) can cause paralysis (often permanent) in only a number of hours. Among those that experience paralysis, 5 to 10 percent die when their breathing muscles become immobilized.

There is no known cure or treatment for polio. It can only be prevented through immunisation.

Since 1988 there has been a global effort to eliminate this disease through the widespread use of polio vaccination. As a result, in 2013, only three countries in the world continue to report sporadic cases of polio. These countries are Afghanistan, Nigeria, and Pakistan. Occasionally, a case of polio is imported into a country where the disease has been already eliminated, and a few secondary cases may occur. Such cases have occurred in Angola, Niger, Chad, the Democratic Republic of the Congo, and southern Sudan.

Recently, there have been outbreaks of polio in Ethiopia, Somalia and Syria.