Three serotypes of poliovirus have been identified – wild poliovirus type 1 (WPV1), type 2 (WPV2), and type 3 (WPV3) – each with a slightly different capsid protein. All three are extremely virulent and produce the same disease symptoms. PV1 is the most commonly encountered form, and the one most closely associated with paralysis. WPV2 was certified as eradicated in 2015 and WPV3 certified as eradicated in 2019.Individuals who are exposed to the virus, either through infection or by immunization via polio vaccine, develop immunity. In immune individuals, IgA antibodies against poliovirus are present in the tonsils and gastrointestinal tract and able to block virus replication; IgG and IgM antibodies against PV can prevent the spread of the virus to motor neurons of the central nervous system. Infection or vaccination with one serotype of poliovirus does not provide immunity against the other serotypes, and full immunity requires exposure to each serotype.A rare condition with a similar presentation, nonpoliovirus poliomyelitis, may result from infections with enteroviruses other than poliovirus.The oral polio vaccine contains weakened viruses that can replicate. On rare occasions, these may be transmitted from the vaccinated person to other people, who may display symptoms of polio. In communities with good vaccine coverage transmission is limited, and the virus dies out. In communities with low vaccine coverage, this weakened virus may continue to circulate. Polio arising from this cause is referred to as circulating vaccine-derived polio (cVDPV) in order to distinguish it from the natural or "wild" poliovirus (WPV).
Etymology
The term derives from the Ancient Greek poliós (πολιός), meaning "grey", myelós (µυελός "marrow"), referring to the grey matter of the spinal cord, and the suffix -itis, which denotes inflammation, i.e., inflammation of the spinal cords grey matter, although a severe infection can extend into the brainstem and even higher structures, resulting in polioencephalitis, resulting in inability to breathe, requiring mechanical assistance such as an iron lung. Research
The Poliovirus Antivirals Initiative was launched in 2007 with the aim of developing antiviral medications for polio, but while several promising candidates were identified, none have progressed beyond Phase II clinical trials. Pocapavir (a capsid inhibitor) and V-7404 (a protease inhibitor) may speed up viral clearance and are being studied for this purpose. References
Further reading
Kluger Jefferey (2004). Splendid Solution: Jonas Salk and the Conquest of Polio. New York: G. P. Putnams Sons. ISBN 978-0-399-15216-0. Oshinsky DM (2005). Polio: An American story. Oxford: Oxford University Press. ISBN 978-0-19-515294-4. polio. Shaffer MM, Bernard S (2005). The death of a disease: a history of the eradication of poliomyelitis. New Brunswick, NJ: Rutgers University Press. ISBN 978-0-8135-3677-4. Shell M (2005). Polio and its aftermath: the paralysis of culture. Cambridge: Harvard University Press. ISBN 978-0-674-01315-5. polio. Wilson DJ (2005). Living with polio: the epidemic and its survivors. Chicago: University of Chicago Press. ISBN 978-0-226-90103-9. Wilson DJ, Silver J (2007). Polio voices: an oral history from the American polio epidemics and worldwide eradication efforts. New York: Praeger. ISBN 978-0-275-99492-1.