Polio causes
Cause
Poliomyelitis is caused by infection with a member of the genus enterovirus known as poliovirus (PV). This group of RNA viruses prefers to inhabit the gastrointestinal tract.[1] PV infects and causes disease in humans alone.[2] Its structure is very simple, composed of a single (+) sense RNA genome enclosed in a protein shell called a capsid.[2] In addition to protecting the virus’s genetic material, the capsid proteins enable poliovirus to infect certain types of cells. Three serotypes of poliovirus have been identified—poliovirus type 1 (PV1), type 2 (PV2), and type 3 (PV3)—each with a slightly different capsid protein.[3] All three are extremely virulent and produce the same disease symptoms.[2] PV1 is the most commonly encountered form, and the one most closely associated with paralysis.[4]
Individuals who are exposed to the virus, either through infection or by immunization with polio vaccine, develop immunity. In immune individuals, IgA antibodies against poliovirus are present in the tonsils and gastrointestinal tract and are 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.[5] Infection or vaccination with one serotype of poliovirus does not provide immunity against the other serotypes, and full immunity requires exposure to each serotype.[5]
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<ref>tag; no text was provided for refs namedSherris - ↑ Katz, Samuel L.; Gershon, Anne A.; Krugman, Saul; Hotez, Peter J. (2004). Krugman's infectious diseases of children. St. Louis: Mosby. pp. 81–97. ISBN 0-323-01756-8.
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