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.
Of the 3 strains of wild poliovirus (type 1, type 2, and type 3), wild poliovirus type 2 was eradicated in 1999 and no case of wild poliovirus type 3 has been found since the last reported case in Nigeria in November 2012.
This reduction is the result of the global effort to eradicate the disease, according to WHO.
Despite the progress achieved since 1988, as long as a single child remains infected with poliovirus, children in all countries are at risk of contracting the disease.
The poliovirus can easily be imported into a polio-free country and can spread rapidly amongst unimmunized populations.
Failure to eradicate polio could result in as many as 200 000 new cases every year, within 10 years, all over the world.
There is no cure for polio, it can only be prevented. Polio vaccine, given multiple times, can protect a child for life.
Key facts
- Polio (poliomyelitis) mainly affects children under 5 years of age.
- 1 in 200 infections leads to irreversible paralysis. Among those paralysed, 5% to 10% die when their breathing muscles become immobilized.
- Cases due to wild poliovirus have decreased by over 99% since 1988, from an estimated 350 000 cases then, to 33 reported cases in 2018.
- As long as a single child remains infected, children in all countries are at risk of contracting polio. Failure to eradicate polio from these last remaining strongholds could result in as many as 200 000 new cases every year, within 10 years, all over the world.
- In most countries, the global effort has expanded capacities to tackle other infectious diseases by building effective surveillance and immunization systems.
