Polio
A highly infectious viral disease preventable by vaccination.
Polio, short for poliomyelitis, is a vaccine-preventable infectious disease caused by the poliovirus. It has existed for thousands of years and became one of the most worrying childhood diseases in the 20th century before the introduction of vaccines in the 1950s led to a rapid decline in incidence. As of October 2023, only Pakistan and Afghanistan remain endemic for wild poliovirus.
- first described
- 1789 by Michael Underwood
- virus identified
- 1909 by Karl Landsteiner
- transmission
- fecal–oral and oral–oral routes
- incubation period
- 3–6 days (nonparalytic); 7–21 days (paralytic)
- vaccine types
- inactivated polio vaccine (IPV) and oral polio vaccine (OPV)
- global cases in 1988
- estimated 350,000
- global cases in 2022
- 30 confirmed
Quick Facts
- Field
- Neurology, infectious disease
- Pronounce
- ˌ · p · oʊ · l · i · oʊ · ˌ · m · aɪ · ə · ' · l · aɪ · t · ᵻ · s
- Symptoms
- Fever, sore throat
- Complications
- Muscle weakness resulting in paralysis; Post-polio syndrome
- Causes
- Poliovirus spread by fecal–oral route
- Risks
- Poor hygiene
- Diagnosis
- Finding the virus in the feces or antibodies in the blood
- Prevention
- Polio vaccine
- Treatment
- No treatment other than supportive care
- Frequency
- 30 (wild) + 856 (vaccine-derived) in 2022
- Types
- Wild PV types 1, 2 & 3; vaccine-derived PV
Facts from the source article.
Lore & Background
Poliomyelitis is caused by the poliovirus, an RNA virus that colonizes the gastrointestinal tract. Approximately 75% of infections are asymptomatic; mild symptoms include sore throat and fever. In about 1% of infections, the virus migrates to the central nervous system, potentially causing nonparalytic meningitis or, in 1 to 5 per 1,000 cases, acute flaccid paralysis. Paralysis most often affects the legs but can involve breathing muscles, leading to death in 2–10% of paralytic cases. Years after recovery, post-polio syndrome may cause slow muscle weakness.
Reader's Guide
Polio's significance lies in its historical impact as a feared childhood disease and its near-eradication through vaccination. The disease is transmitted person-to-person via fecal–oral or oral–oral routes, with infected individuals spreading the virus for up to six weeks even without symptoms. Two vaccine types exist: injected inactivated polio vaccine (IPV) and oral live attenuated vaccine (OPV). The traditional OPV rarely reverted to a virulent form, leading to the development of a genetically stable oral vaccine (nOPV2) granted full licensure by the World Health Organization in December 2023. Global incidence dropped from an estimated 350,000 cases in 1988 to 30 confirmed cases in 2022, confined to three countries. No specific treatment exists once infected; prevention relies on multiple vaccine doses for lifelong protection.
Did You Know?
- The term 'poliomyelitis' was first used in 1874 by German physician Adolf Kussmaul.
- Polio occurs naturally only in humans and is highly infectious.
- About 1 in 1,000 infections progress to paralytic disease, causing acute flaccid paralysis.
- The oral polio vaccine can, in rare cases, revert to a virulent form in communities with low vaccine coverage.
More in Viral Infections 1-20
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