Poliomyelitis

Poliomyelitis is an infectious disease caused by poliovirus, a member of the genus Enterovirus. The virus invades the nervous system and can cause total paralysis within hours of symptom onset. The disease occurs naturally only in humans and is characterized by inflammation of the spinal cord's grey matter, from which the name derives.

Approximately 75% of poliovirus infections are asymptomatic, making widespread transmission possible without recognition. When symptoms occur, they range from mild manifestations including sore throat and fever to more severe presentations such as headache, neck stiffness, and paresthesia, which typically resolve within one to two weeks. One in 200 infections leads to irreversible paralysis, usually affecting the legs, and among those paralyzed, 5-10% die when their breathing muscles become immobilized. Years after recovery, some individuals develop post-polio syndrome, characterized by slow progression of muscle weakness similar to the initial infection.

Wild poliovirus cases have decreased by over 99% since 1988, from an estimated 350,000 cases in more than 125 endemic countries to only two endemic countries as of 2025 (Pakistan and Afghanistan). Wild poliovirus type 2 was eradicated in 1999 and type 3 in 2020, leaving wild poliovirus type 1 as the remaining strain in endemic areas. The WHO Regions of the Americas (1994), Western Pacific (2000), European (2002), and South-East Asia (2014) have been certified polio-free, indicating interruption of wild poliovirus transmission in these regions.

Poliovirus is transmitted primarily through the fecal-oral route, either by person-to-person spread or via contaminated food or water. Less frequently, transmission occurs through the oral-oral route. The virus multiplies in the intestine and can be excreted in feces for up to six weeks, even in the absence of symptoms. The incubation period is usually 7-10 days but can range from 4-35 days, with peak infectiousness occurring 7-10 days before and after symptom appearance.

Polio mainly affects children under 5 years of age, who constitute the majority of cases. However, anyone of any age who is unvaccinated can contract the disease. Adults are more likely than children to develop symptomatic disease and severe manifestations. Pregnancy and conditions that compromise immune function increase the risk of infection.

There is no cure for polio; it can only be prevented through vaccination. Polio vaccine, administered multiple times, can protect a child for life. Two vaccines are available: oral polio vaccine and inactivated polio vaccine. The Global Polio Eradication Initiative, launched in 1988, coordinates international eradication efforts through national governments, WHO, Rotary International, CDC, UNICEF, the Bill & Melinda Gates Foundation, and Gavi.

Polio surveillance requires maintaining high vaccination coverage and sensitive disease monitoring, as the virus can be imported into polio-free countries and spread rapidly among unimmunized populations. Failure to sustain eradication efforts would result in global resurgence of the disease. Continued implementation of eradication strategies and transition planning are essential to preserve public health infrastructure built during the eradication effort.

1. 1 WHO Health Topics. Poliomyelitis (polio).
2. 2 WHO Fact Sheet. Poliomyelitis.
3. 3 WHO Q&A. Poliomyelitis.
4. 4 Wikidata. poliomyelitis.
5. 5 Wikipedia. Polio - Wikipedia.

ICD-10

A80

ICD-11

1C81

Total cases

30

Total deaths

1

Peak month

2011-10

Coverage

3 reporting countries · 2000-01-01 → 2026-05-02