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| __NOTOC__
| | #REDIRECT [[Smallpox virus]] |
| {{Smallpox}}
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| {{CMG}}; {{AE}} {{JS}}
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| ==Overview==
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| [[Smallpox]] is caused by the [[variola]] virus.
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| ==Taxonomy==
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| [[Viruses]]; [[DNA virus|dsDNA]]; [[Poxviridae]]; Chordopoxvirinae; [[Orthopoxvirus]]; Variola vera
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| ==Biology==
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| [[Variola virus]] is a [[orthopoxvirus]], from the family [[Poxviridae]], the largest [[viruses]] to [[infect]] humans. It is a 200-400 nm dsDNA virus, lacking icosahedral symmetry. The other [[viruses]] of the family [[Poxviridae]] include:<ref name="MooreSeward2006">{{cite journal|last1=Moore|first1=Zack S|last2=Seward|first2=Jane F|last3=Lane|first3=J Michael|title=Smallpox|journal=The Lancet|volume=367|issue=9508|year=2006|pages=425–435|issn=01406736|doi=10.1016/S0140-6736(06)68143-9}}</ref>
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| * [[Vaccinia virus]]
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| * [[Molluscum contagiosum virus]]
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| * [[Cowpox virus]]
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| * [[Monkeypox virus]]
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| The [[viral]] structure includes:<ref>{{cite book | last = Fields | first = Bernard | title = Fields virology | publisher = Wolters Kluwer Health/Lippincott Williams & Wilkins | location = Philadelphia | year = 2007 | isbn = 0781760607 }}</ref><ref name="pmid8184534">{{cite journal| author=Massung RF, Liu LI, Qi J, Knight JC, Yuran TE, Kerlavage AR et al.| title=Analysis of the complete genome of smallpox variola major virus strain Bangladesh-1975. | journal=Virology | year= 1994 | volume= 201 | issue= 2 | pages= 215-40 | pmid=8184534 | doi=10.1006/viro.1994.1288 | pmc= |url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=8184534 }} </ref><ref name="pmid8661439">{{cite journal| author=Massung RF, Loparev VN, Knight JC, Totmenin AV, Chizhikov VE, Parsons JM et al.| title=Terminal region sequence variations in variola virus DNA. | journal=Virology | year= 1996 | volume= 221 | issue= 2 |pages= 291-300 | pmid=8661439 | doi=10.1006/viro.1996.0378 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=8661439 }} </ref>
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| * [[Outer membrane]]
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| * 2 lateral bodies
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| * 1 dsDNA molecule in its core containing 186,999 base pairs
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| [[Variola virus]] [[genes]] are similar to the ones of [[vaccinia virus]]. Since there is cross-protection between poxviruses, it was possible to use the second as a [[vaccine]] for [[smallpox virus]].<ref name="ShchelkunovResenchuk1993">{{cite journal|last1=Shchelkunov|first1=Sergei N.|last2=Resenchuk|first2=Sergei M.|last3=Totmenin|first3=Alexei V.|last4=Blinov|first4=Vladimir M.|last5=Marennikova|first5=Svetlana S.|last6=Sandakhchiev|first6=Lev S.|title=Comparison of the genetic maps of variola and vaccinia viruses|journal=FEBS Letters|volume=327|issue=3|year=1993|pages=321–324|issn=00145793|doi=10.1016/0014-5793(93)81013-P}}</ref>
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| There are 2 forms of [[variola virus]]:
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| * Variola major
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| * Variola minor
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| Both [[strains]] of the [[virus]] share a large amount of [[genome]], yet they differ clinically. This leads to the assumption that the difference in [[virulence]] resides in alternate [[gene expression]].<ref name="MooreSeward2006">{{cite journal|last1=Moore|first1=Zack S|last2=Seward|first2=Jane F|last3=Lane|first3=J Michael|title=Smallpox|journal=The Lancet|volume=367|issue=9508|year=2006|pages=425–435|issn=01406736|doi=10.1016/S0140-6736(06)68143-9}}</ref><ref name=WHO>{{cite web | title = Smallpox and its Eradication | url = http://apps.who.int/iris/bitstream/10665/39485/1/9241561106.pdf?ua=1 }}</ref>
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| Poxviruses survive in cold and dry environments being able to survive in the [[aerosol]] form, and are killed by hospital disinfectants and [[UV light]].<ref name="MooreSeward2006">{{cite journal|last1=Moore|first1=Zack S|last2=Seward|first2=Jane F|last3=Lane|first3=J Michael|title=Smallpox|journal=The Lancet|volume=367|issue=9508|year=2006|pages=425–435|issn=01406736|doi=10.1016/S0140-6736(06)68143-9}}</ref><ref name=WHO>{{cite web | title = Smallpox and its Eradication | url = http://apps.who.int/iris/bitstream/10665/39485/1/9241561106.pdf?ua=1 }}</ref><ref name="pmid4371586">{{cite journal| author=Thomas G| title=Air sampling of smallpox virus. | journal=J Hyg (Lond) | year= 1974 | volume= 73 | issue= 1 | pages= 1-7 | pmid=4371586 | doi= | pmc=PMC2130554 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=4371586 }} </ref><ref name="pmid13904777">{{cite journal| author=HARPER GJ| title=Airborne micro-organisms: survival tests with four viruses. | journal=J Hyg (Lond) | year= 1961 | volume= 59 | issue= | pages= 479-86 | pmid=13904777 | doi= | pmc=PMC2134455 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=13904777 }} </ref>
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| Unlike other [[DNA viruses]], poxviruses replicate within the [[cytoplasm]] of the host cell. In order to replicate, poxviruses produce a variety of specialized [[proteins]] not produced by other [[DNA viruses]], the most important of which is a viral-associated DNA-dependent RNA polymerase.
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| ==Origin==
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| ==Tropism==
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| Little is known about the mechanism responsible for host species tropism of smallpox virus. The virus is known to bind mammalian cells unspecifically. There appears to be no particular extracellular receptors involved in viral internalization and initial transcription. However, intracellular availability of trans-acting factors and capacity to block host cell antiviral response, such as interferon pathway, are though to be important intracellular factors determining viral tropism. The overall immune response by the host towards the virus will be the key determinant of the outcome of the infection and the potential transmission to other hosts.
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| ==Natural reservoir==
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| [[Humans]] are the only [[natural reservoir]] of [[smallpox virus]].<ref name=CDC>{{cite web | title = Smallpox disease overview | url = http://www.bt.cdc.gov/agent/smallpox/overview/disease-facts.asp }}</ref>
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| ==References==
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| {{Reflist|2}}
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| [[Category:Needs content]]
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| [[Category:Disease]]
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| [[Category:Infectious disease]]
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| [[Category:Pediatrics]]
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| [[Category:Smallpox]]
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| [[Category:Viral diseases]]
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| [[Category:Poxviruses]]
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| {{WH}}
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| {{WS}}
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