Smallpox causes: Difference between revisions
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==Biology== | ==Biology== | ||
[[Variola virus]] is | [[Variola virus]] is an [[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> | ||
* [[Vaccinia virus]] | * [[Vaccinia virus]] | ||
* [[Molluscum contagiosum virus]] | * [[Molluscum contagiosum virus]] | ||
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* [[Monkeypox virus]] | * [[Monkeypox virus]] | ||
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> | 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> | ||
* [[Outer membrane]] | * 1 [[Outer membrane]] | ||
* 2 lateral bodies | * 2 lateral bodies | ||
* 1 dsDNA molecule in its core containing 186,999 base pairs | * 1 [[dsDNA virus|dsDNA]] [[molecule]] in its core, containing 186,999 base pairs | ||
[[Variola virus]] [[genes]] are similar to the ones of [[vaccinia virus]]. Since there is cross-protection between | [[Variola virus]] [[genes]] are similar to the ones of [[vaccinia virus]]. Since there is cross-protection between [[poxvirus]]es, 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> | ||
There are 2 forms of [[variola virus]]: | There are 2 forms of [[variola virus]]: | ||
| Line 28: | Line 28: | ||
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> | 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> | ||
[[Poxvirus]]es survive in cold and dry environments being able to survive in the [[aerosol]]ed 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> | |||
Unlike other [[DNA viruses]], | Unlike other [[DNA viruses]], [[poxvirus]]es replicate within the [[cytoplasm]] of the host cell. In order to replicate, [[poxvirus]]es 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. | ||
==Origin== | ==Origin== | ||
Revision as of 04:11, 13 July 2014
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]
Overview
Smallpox is caused by the variola virus, a dsDNA virus of the Poxviridae family. There are two forms of this virus with different virulences, represented on the discrepancy in respective death rates. The virus survives in the cold and aerosoled environments, which explains its oral transmission among humans, which are it's only host species. Unlike other DNA viruses, it replicates within the cytoplasm, to which it shows tropism.
Taxonomy
Viruses; dsDNA; Poxviridae; Chordopoxvirinae; Orthopoxvirus; Variola vera
Biology
Variola virus is an 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:[1]
The viral structure includes:[2][3][4]
- 1 Outer membrane
- 2 lateral bodies
- 1 dsDNA molecule in its core, containing 186,999 base pairs
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.[5]
There are 2 forms of variola virus:
- Variola major
- Variola minor
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.[1][6]
Poxviruses survive in cold and dry environments being able to survive in the aerosoled form, and are killed by hospital disinfectants and UV light.[1][6][7][8]
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.
Origin
The date of the origin of the smallpox virus is not settled. It most likely evolved from a rodent virus between 68,000 and 16,000 years ago.[9][10] This broad range of dates is due to the different records used to calibrate the molecular clock. It appears that the smallpox virus derived from a remote zoonosis from another animal host, that is today extinct.[11]
Tropism
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 viral capacity to block host cells antiviral response, such as the 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.[11]
Natural reservoir
Humans are the only natural reservoir of smallpox virus.[12]
References
- ↑ 1.0 1.1 1.2 Moore, Zack S; Seward, Jane F; Lane, J Michael (2006). "Smallpox". The Lancet. 367 (9508): 425–435. doi:10.1016/S0140-6736(06)68143-9. ISSN 0140-6736.
- ↑ Fields, Bernard (2007). Fields virology. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. ISBN 0781760607.
- ↑ Massung RF, Liu LI, Qi J, Knight JC, Yuran TE, Kerlavage AR; et al. (1994). "Analysis of the complete genome of smallpox variola major virus strain Bangladesh-1975". Virology. 201 (2): 215–40. doi:10.1006/viro.1994.1288. PMID 8184534.
- ↑ Massung RF, Loparev VN, Knight JC, Totmenin AV, Chizhikov VE, Parsons JM; et al. (1996). "Terminal region sequence variations in variola virus DNA". Virology. 221 (2): 291–300. doi:10.1006/viro.1996.0378. PMID 8661439.
- ↑ Shchelkunov, Sergei N.; Resenchuk, Sergei M.; Totmenin, Alexei V.; Blinov, Vladimir M.; Marennikova, Svetlana S.; Sandakhchiev, Lev S. (1993). "Comparison of the genetic maps of variola and vaccinia viruses". FEBS Letters. 327 (3): 321–324. doi:10.1016/0014-5793(93)81013-P. ISSN 0014-5793.
- ↑ 6.0 6.1 "Smallpox and its Eradication" (PDF).
- ↑ Thomas G (1974). "Air sampling of smallpox virus". J Hyg (Lond). 73 (1): 1–7. PMC 2130554. PMID 4371586.
- ↑ HARPER GJ (1961). "Airborne micro-organisms: survival tests with four viruses". J Hyg (Lond). 59: 479–86. PMC 2134455. PMID 13904777.
- ↑ Esposito, J. J. (2006). "Genome Sequence Diversity and Clues to the Evolution of Variola (Smallpox) Virus". Science. 313 (5788): 807–812. doi:10.1126/science.1125134. ISSN 0036-8075.
- ↑ Li, Y.; Carroll, D. S.; Gardner, S. N.; Walsh, M. C.; Vitalis, E. A.; Damon, I. K. (2007). "On the origin of smallpox: Correlating variola phylogenics with historical smallpox records". Proceedings of the National Academy of Sciences. 104 (40): 15787–15792. doi:10.1073/pnas.0609268104. ISSN 0027-8424.
- ↑ 11.0 11.1 McFadden, Grant (2005). "Poxvirus tropism". Nature Reviews Microbiology. 3 (3): 201–213. doi:10.1038/nrmicro1099. ISSN 1740-1526.
- ↑ "Smallpox disease overview".