Poliomyelitis is a disease caused by infection with the poliovirus. The virus spreads by:
- Direct person-to-person contact
- Contact with infected mucus or phlegm from the nose or mouth
- Contact with infected feces
The virus enters through the mouth and nose, multiplies in the throat and intestinal tract, and then is absorbed and spread through the blood and lymph system. The time from being infected with the virus to developing symptoms of disease (incubation) ranges from 5 - 35 days (average 7 - 14 days). Most people do not develop symptoms.
- Lack of immunization against polio
- Travel to an area that has experienced a polio outbreak
Outbreaks can still occur in the developed world, usually in groups of people who have not been vaccinated. Polio often occurs after someone travels to a region where there has been an outbreak of disease. As a result of a massive, global vaccination campaign over the past 20 years, polio exists only in a few countries in Africa and Asia. These include Afghanistan, Cameroon, Equatorial Guinea, Ethiopia, Iraq, Israel, Nigeria, Pakistan, Somalia, and Syria.