Poliomyelitis (polio)
Since 2000, the Western Pacific Region has maintained polio-free status.
Poliomyelitis is a highly infectious disease caused by a poliovirus. It mainly affects children under 5 years of age but also can affect older age groups. Polioviruses are spread by faecal-to-oral and oral-to-oral transmission. Lack of access to clean water and adequate sanitation is a major risk factor for transmission.
Most infected people have no symptoms but can transmit infection to others by excreting the virus in their faeces. It is estimated that one in 200 infections leads to irreversible paralysis. Among those paralysed, 5–10% will die when their breathing muscles become immobilized.
There is no cure for polio; however, it can be prevented by vaccination.
Poliovirus is highly infectious. The incubation period is usually 7–10 days but can range from 4–35 days.
The virus enters the body through the mouth and multiplies in the intestine. It then invades the nervous system. Up to 90% of those infected experience no or mild symptoms and the disease usually goes unrecognized.
In others, initial symptoms include fever, fatigue, headache, vomiting, stiffness in the neck, and pain in the limbs. These symptoms usually last for 2–10 days and most recovery is complete in almost all cases. However, in the remaining proportion of cases the virus causes paralysis, usually of the legs, which is most often permanent. Of those paralysed, 5-10% die when their breathing muscles become immobilized.
There is no cure for polio; it can only be prevented by immunization. The polio vaccine, given multiple times, can protect a child for life. If enough people in a community are immunized against polio, the virus will be deprived of susceptible hosts and will die out. High levels of vaccination coverage must be maintained to stop transmission and prevent outbreaks occurring.
WHO is continuing to work with countries in the Region to stop the use of oral polio vaccine (OPV) and use only inactivated poliovirus vaccine (IPV) in routine immunization schedules, to prevent the emergence and circulation of vaccine-derived polioviruses in the future.
