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| __NOTOC__
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| {{Polio}}
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| {{CMG}}
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| ==Overview==
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| Polio is a highly infectious disease caused by Poliovirus that invades the [[nervous system]]. Poliovirus are small (27–30 nm), nonenveloped viruses with [[capsid]]s enclosing a single-stranded, positive-sense [[RNA]] genome about 7,500 nucleotides long. Person-to-person spread of poliovirus via the fecal-oral route is the most important route of transmission, although the oral-oral route may account for some cases.
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| ==Taxonomy==
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| [[Virus]]es; [[dsDNA]] viruses, no [[RNA]] stage; [[Polyomaviridae]]<ref name=NCBI>{{cite web | title = Polyomavirus | url = http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=10624 }}</ref>
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| ==Biology==
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| {| style="float: right;"
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| | [[File:Polio EM PHIL 1875 lores.PNG|200px|thumb|none|A Transmission electron microscopy of poliovirus<SMALL> ''Image provided by the CDC [http://phil.cdc.gov/phil/details.asp Centers for Disease Control and Prevention] ''<ref>{{Cite web | title = http://phil.cdc.gov/phil/details.asp | url = http://phil.cdc.gov/phil/details.asp}}</ref></SMALL>]]
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| [[Poliovirus]] is a member of the [[enterovirus]] subgroup, family [[Picornaviridae]]. Enteroviruses are transient inhabitants of the gastrointestinal tract, and are stable at acid pH. Picornaviruses are small, ether-insensitive viruses with an RNA genome.<ref name=CDC>{{cite web | title = Polyomavirus | url = http://www.cdc.gov/vaccines/pubs/pinkbook/downloads/polio.pdf }}</ref>
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| There are three poliovirus [[serotype]] (P1, P2, and P3). There is minimal heterotypic [[immunity]] between the three [[serotype]]s. That is, immunity to one [[serotype]] does not produce significant immunity to the other serotypes. The poliovirus is rapidly inactivated by heat, formaldehyde, chlorine, and ultraviolet light.<ref name=CDC>{{cite web | title = Polyomavirus | url = http://www.cdc.gov/vaccines/pubs/pinkbook/downloads/polio.pdf }}</ref>
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| [[Poliomyelitis]] is caused by infection with a member of the [[genus]] ''[[enterovirus]]'' known as [[poliovirus]] (PV). This group of [[RNA virus]]es prefers to inhabit the [[gastrointestinal tract]]. PV [[pathogen|infects and causes disease]] in humans alone. Its [[Virus#Structure|structure]] is very simple, composed of a single [[sense (molecular biology)|(+) sense]] [[RNA]] [[genome]] enclosed in a protein shell called a [[capsid]]. In addition to protecting the virus’s genetic material, the capsid proteins enable poliovirus to infect certain types of cells. Three [[serovar|serotype]]s of poliovirus have been identified—poliovirus type 1 (PV1), type 2 (PV2), and type 3 (PV3)—each with a slightly different capsid protein.<ref>{{cite book |author=Katz, Samuel L.; Gershon, Anne A.; Krugman, Saul; Hotez, Peter J. |title=Krugman's infectious diseases of children |publisher=Mosby |location=St. Louis |year=2004 |pages=81–97 |isbn=0-323-01756-8 |oclc= |doi=}}</ref> All three are extremely [[virulence|virulent]] and produce the same disease symptoms. PV1 is the most commonly encountered form, and the one most closely associated with paralysis.
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| Individuals who are exposed to the virus, either through infection or by [[immunization]] with polio vaccine, develop [[immunity (medical)|immunity]]. In immune individuals, [[IgA]] [[antibodies]] against poliovirus are present in the [[tonsil]]s 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]]. Infection or vaccination with one serotype of poliovirus does not provide immunity against the other serotypes, and full immunity requires exposure to each serotype.
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| ==Natural Reservoir==
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| Humans are the only known reservoir of poliovirus, which is transmitted most frequently by persons with inapparent infections. There is no asymptomatic carrier state except in immune deficient persons.
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| ==References==
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| {{Reflist|2}}
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| [[Category:Needs overview]]
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| [[Category:Disease]]
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| [[Category:Infectious disease]]
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| [[Category:Primary care]]
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| {{WH}}
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| {{WS}}
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