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Poliomyelitis (/ ˌ p oʊ l i oʊ ˌ m aɪ ə ˈ l aɪ t ɪ s / POH-lee-oh-MY-ə-LY-tiss), commonly shortened to polio, is an infectious disease caused by the poliovirus. [1] Approximately 75% of cases are asymptomatic; [5] mild symptoms which can occur include sore throat and fever; in a proportion of cases more severe symptoms develop such as headache, neck stiffness, and paresthesia.
Type 3 (WPV3) is last known to have caused polio in 2012, and was declared eradicated in 2019. [59] All wild-virus cases since that date have been due to type 1 (WPV1). [60] As of August 2024, Afghanistan and Pakistan are the only two countries where the disease is still classified as endemic.
The history of polio (poliomyelitis) infections began during prehistory. Although major polio epidemics were unknown before the 20th century, [1] the disease has caused paralysis and death for much of human history. Over millennia, polio survived quietly as an endemic pathogen until the 1900s when major epidemics began to occur in Europe. [1]
The virus infects the throat and intestines, and can cause flu-like symptoms. Paralysis from the polio virus is rare. This year, polio cases have been detected in New York state, London and Jerusalem.
Health authorities have become more successful in reducing the number of cases caused by the wild polio virus. Vaccine-related cases now cause the majority of infections worldwide.
In extreme cases polio can cause paralysis, usually in the legs, although movement typically comes back within a few weeks or months. However, it can be life-threatening if it paralyses the ...
But it contains weakened, live polio virus and in very rare cases can spread and cause polio in unvaccinated people. In even rarer instances, the live virus from the vaccine can mutate into a new form capable of starting new outbreaks. Health authorities have become more successful in reducing the number of cases caused by the wild polio virus.
In 1949, John F. Enders (1897–1985) Thomas Weller (1915–2008), and Frederick Robbins (1916–2003) grew polio virus for the first time in cultured human embryo cells, the first virus to be grown without using solid animal tissue or eggs. Infections by poliovirus most often cause the mildest of symptoms.