Lassa fever causes: Difference between revisions

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__NOTOC__
__NOTOC__
<div style="float: right;">
{{Taxobox
| name            = ''Lassa Virus (LASV)''
| image            = Lassa virus.JPG
| image_width      = 200 px
| image_caption    = [[Transmission electron microscopy|TEM]] [[micrograph]] of ''Lassa virus'' [[Virion#Structure|virions]].
| virus_group      = v
| ordo            = ''Unassigned''
| familia          = ''[[Arenavirus|Arenaviridae]]''
| genus            = ''[[Arenavirus]]''
| species          = '''''Lassa virus'''''
}}</div>
{{Lassa fever}}
{{Lassa fever}}
{{CMG}}; {{AE}} {{Ammu}}
{{CMG}}; {{AE}} {{Ammu}}
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Lassa fever is caused by the ''[[Lassa virus]]'', a member of the [[Arenaviridae]] family. It is an [[enveloped virus|enveloped]], [[single-stranded]], bisegmented [[RNA]] virus. Mastomysrodents shed the [[virus]] in [[urine]] and droppings. The direct contact with these materials or [[ingestion]] or [[inhalation]], can lead to [[infection]]. Lassa virus enters the [[cell]] by the receptor-mediated [[endocytosis]] and undergoes very rapid [[replication]] and manifest the [[disease]].
Lassa fever is caused by the ''[[Lassa virus]]'', a member of the [[Arenaviridae]] family. It is an [[enveloped virus|enveloped]], [[single-stranded]], bisegmented [[RNA]] virus. Mastomysrodents shed the [[virus]] in [[urine]] and droppings. The direct contact with these materials or [[ingestion]] or [[inhalation]], can lead to [[infection]]. Lassa virus enters the [[cell]] by the receptor-mediated [[endocytosis]] and undergoes very rapid [[replication]] and manifest the [[disease]].


==Virus==
==Causes==
===Taxonomy===
===Taxonomy===
* [[Viruses]]; [[ssRNA viruses]]; [[ssRNA negative-strand viruses]]; [[Arenaviridae]]; [[Mammarenavirus]] <ref>{{cite web | title = Taxonomy browser (Lassavirus) | url = http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=11621&lvl=3&keep=1&srchmode=1&unlock&lin=s}}</ref>
* [[Viruses]]; [[ssRNA viruses]]; [[ssRNA negative-strand viruses]]; [[Arenaviridae]]; [[Mammarenavirus]] <ref>{{cite web | title = Taxonomy browser (Lassavirus) | url = http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=11621&lvl=3&keep=1&srchmode=1&unlock&lin=s}}</ref>
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* The Arenaviridae are a family of [[viruses]] whose members are generally associated with rodent-transmitted diseases in [[humans]]. Each [[virus]] usually is associated with a particular [[rodent]] host species in which it is maintained.
* The Arenaviridae are a family of [[viruses]] whose members are generally associated with rodent-transmitted diseases in [[humans]]. Each [[virus]] usually is associated with a particular [[rodent]] host species in which it is maintained.


===Structure and genome===
===Structure===
* Lassa viruses are enveloped, [[single-stranded]], bisegmented, ambisense [[RNA viruses]]. Their genome<ref name="pmid10615121">{{cite journal| author=| title=Genome:The autobiography of a species in 23 chapters | journal=Nat Genet | year= 2000 | volume= 24 | issue= 1 | pages= 21 | pmid=10615121 | doi=10.1038/71638 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10615121  }} </ref> is contained in two RNA segments that code for two proteins each, one in each sense, for a total of four viral proteins.<ref name="pmid17143722">{{cite journal| author=Moshkoff DA, Salvato MS, Lukashevich IS| title=Molecular characterization of a reassortant virus derived from Lassa and Mopeia viruses. | journal=Virus Genes | year= 2007 | volume= 34 | issue= 2 | pages= 169-76 | pmid=17143722 | doi=10.1007/s11262-006-0050-3 | pmc=PMC1892610 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=17143722  }} </ref> The large segment encodes a small zinc-binding protein (Z) that regulates transcription and replication,<ref name="pmid11533204">{{cite journal| author=Cornu TI, de la Torre JC| title=RING finger Z protein of lymphocytic choriomeningitis virus (LCMV) inhibits transcription and RNA replication of an LCMV S-segment minigenome. | journal=J Virol | year= 2001 | volume= 75 | issue= 19 | pages= 9415-26 | pmid=11533204 | doi=10.1128/JVI.75.19.9415-9426.2001 | pmc=PMC114509 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=11533204  }} </ref><ref name="pmid9281522">{{cite journal| author=Djavani M, Lukashevich IS, Sanchez A, Nichol ST, Salvato MS| title=Completion of the Lassa fever virus sequence and identification of a RING finger open reading frame at the L RNA 5' End. | journal=Virology | year= 1997 | volume= 235 | issue= 2 | pages= 414-8 | pmid=9281522 | doi=10.1006/viro.1997.8722 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=9281522  }} </ref> and also has the [[RNA polymerase]] (L). The small segment encodes the [[nucleoprotein]] (NP) and the surface [[glycoprotein precursor]] ([[GP]], also known as the viral spike), which is proteolytically cleaved into the [[envelope]] [[glycoproteins]] [[GP1]] and [[GP2]] that bind to the alpha-dystroglycan [[receptor]] and mediate [[host]] cell entry.<ref name="pmid11119613">{{cite journal| author=Smelt SC, Borrow P, Kunz S, Cao W, Tishon A, Lewicki H et al.| title=Differences in affinity of binding of lymphocytic choriomeningitis virus strains to the cellular receptor alpha-dystroglycan correlate with viral tropism and disease kinetics. | journal=J Virol | year= 2001 | volume= 75 | issue= 1 | pages= 448-57 | pmid=11119613 | doi=10.1128/JVI.75.1.448-457.2001 | pmc=PMC113937 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=11119613  }} </ref>
* Lassa virus is an enveloped, [[single-stranded]], bisegmented, ambisense [[RNA virus]].
[[File:Lassa fever micro.png|none|thumb|500px|Outbreak Distribution Map Lassa Fever CDC.png<ref name="CDC Arenaviridea">{{Cite web | title = Center for Disease Control and Prevention (CDC) Arena virus | url =  http://www.cdc.gov/vhf/virus-families/arenaviridae.html}}</ref>]]
* [[Lassa fever]] causes hemorrhagic [[fever]] frequently in [[immunosuppressed]] patients. Replication for [[Lassa virus]] is very rapid and also demonstrates temporal control in replication.<ref name="pmid16629503">{{cite journal| author=Lashley FR| title=Emerging infectious diseases at the beginning of the 21st century. | journal=Online J Issues Nurs | year= 2006 | volume= 11 | issue= 1 | pages= 2 | pmid=16629503 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16629503  }} </ref> The first replication step is transcription of [[mRNA]] copies of the negative- or minus-sense genome. This ensures an adequate supply of viral proteins for subsequent steps of replication, as the NP and L proteins are translated from the [[mRNA]]. The positive- or plus-sense [[genome]], then makes viral complementary [[RNA]] (vcRNA)copies of itself. The [[RNA]] copies are a template for producing negative-sense progeny, but [[mRNA]] is also synthesized from it. The [[mRNA]] synthesized from [[vcRNA]] are translated to make the GP and Z proteins. This temporal control allows the spike proteins to be produced last, and therefore, delay recognition by the host [[immune system]].
* [[Nucleotide]] studies of the [[genome]] have shown that Lassa has four lineages: three found in Nigeria and the fourth in Guinea, Liberia, and Sierra Leone. The Nigerian strains seem likely to have been ancestral to the others but additional work is required to confirm this.<ref name="pmid10888638">{{cite journal| author=Bowen MD, Rollin PE, Ksiazek TG, Hustad HL, Bausch DG, Demby AH et al.| title=Genetic diversity among Lassa virus strains. | journal=J Virol | year= 2000 | volume= 74 | issue= 15 | pages= 6992-7004 | pmid=10888638 | doi= | pmc=PMC112216 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10888638  }} </ref>.


===Receptors===
* The [[Lassa virus]] gains entry into the [[host]] cell by means of the [[cell-surface receptor]] the alpha-[[dystroglycan]] (alpha-DG),<ref name="pmid10888638">{{cite journal| author=Bowen MD, Rollin PE, Ksiazek TG, Hustad HL, Bausch DG, Demby AH et al.| title=Genetic diversity among Lassa virus strains. | journal=J Virol | year= 2000 | volume= 74 | issue= 15 | pages= 6992-7004 | pmid=10888638 | doi= | pmc=PMC112216 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10888638  }} </ref> a versatile [[receptor]] for [[protein]]s of the [[extracellular matrix]]. It shares this [[receptor]] with the prototypic Old World [[arenavirus]] [[lymphocytic choriomeningitis]] virus. [[Receptor]] recognition depends on a specific sugar modification of alpha-dystroglycan by a group of [[glycosyltransferases]] known as the LARGE [[proteins]]. Specific variants of the [[genes]] encoding these [[proteins]] appear to be under positive selection in West Africa where Lassa is endemic. [[Alpha-dystroglycan]] is also used as a [[receptor]] by [[viruses]] of the New World clade C [[arenaviruses]] (Oliveros and Latino viruses). In contrast, the New World [[arenaviruses]] of clades A and B, which include the important [[viruses]] Machupo, Guanarito, Junin, and Sabia in addition to the non pathogenic Amapari virus, use the [[transferrin]] receptor 1. A small aliphatic amino acid at the [[GP1]] [[glycoprotein]] [[amino acid]] position 260 is required for high-affinity binding to [[alpha-DG]]. In addition, [[GP1]] [[amino acid]] position 259 also appears to be important, since all [[arenaviruses]] showing high-affinity [[alpha-DG]] binding possess a bulky aromatic [[amino acid]] ([[tyrosine]] or [[phenylalanine]]) at this position.
* Unlike most enveloped viruses which use [[clathrin]] coated pits for cellular entry and bind to their [[receptors]] in a pH dependent fashion, Lassa and [[lymphocytic choriomeningitis virus]] instead use an [[endocytotic pathway]] independent of [[clathrin]], [[caveolin]], [[dynamin]] and [[actin]]. Once within the [[cell]] the [[viruses]] are rapidly delivered to [[endosomes]] via vesicular trafficking albeit one that is largely independent of the small GTPases Rab5 and Rab7. On contact with the [[endosome]] pH-dependent [[membrane fusion]] occurs mediated by the [[envelope]] [[glycoprotein]], which at the lower [[pH]] of the [[endosome]] binds the [[lysosome]] protein [[LAMP1]] which results in [[membrane]] [[fusion]] and escape from the [[endosome]].


===Life cycle===
===Genome===
* The [[life cycle]] of Lassa virus is similar to the Old World [[arenaviruses]]<ref name=Wikipedia>{{cite web | title = Wikipedia lassa virus | url =http://en.wikipedia.org/wiki/Lassa_virus }}</ref>. Lassa virus enters the [[cell]] by the receptor-mediated [[endocytosis]]. Which [[endocytotic pathway]] is used is not known yet, but at least the cellular entry is sensitive to [[cholesterol]] depletion. It was reported that [[virus]] internalization is limited upon [[cholesterol]] depletion. The [[receptor]] used for [[cell entry]] is [[alpha-dystroglycan]], a highly conserved and ubiquitously expressed [[cell]] surface [[receptor]] for extracellular [[matrix proteins]].
*Lassa virus genome is contained in two RNA segments, each of which encodes 2 viral proteins (total 4 viral proteins)<ref name="pmid10615121">{{cite journal| author=| title=Genome:The autobiography of a species in 23 chapters | journal=Nat Genet | year= 2000 | volume= 24 | issue= 1 | pages= 21 | pmid=10615121 | doi=10.1038/71638 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10615121  }} </ref><ref name="pmid17143722">{{cite journal| author=Moshkoff DA, Salvato MS, Lukashevich IS| title=Molecular characterization of a reassortant virus derived from Lassa and Mopeia viruses. | journal=Virus Genes | year= 2007 | volume= 34 | issue= 2 | pages= 169-76 | pmid=17143722 | doi=10.1007/s11262-006-0050-3 | pmc=PMC1892610 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=17143722 }} </ref>
* [[Dystroglycan]], which is later cleaved into [[alpha-dystroglycan]] and [[beta-dystroglycan]] is originally expressed in most [[cells]] to mature [[tissues]], and it provides molecular link between the [[ECM]] and the [[actin]]-based [[cytoskeleton]]<ref name="pmid18182084">{{cite journal| author=Rojek JM, Kunz S| title=Cell entry by human pathogenic arenaviruses. | journal=Cell Microbiol | year= 2008 | volume= 10 | issue= 4 | pages= 828-35 | pmid=18182084 | doi=10.1111/j.1462-5822.2007.01113.x | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=18182084 }} </ref>. After [[virus]] enters the [[cell]] by [[alpha-dystroglycan]] mediated [[endocytosis]], low-[[pH]] environment triggers [[pH]]-dependent [[membrane fusion]] and releases [[RNP]] (viral [[ribonucleoprotein]]) complex into the [[cytoplasm]].
**The large segment encodes RNA polymerase (L) and a small zinc-binding protein (Z) that regulates transcription and replication<ref name="pmid11533204">{{cite journal| author=Cornu TI, de la Torre JC| title=RING finger Z protein of lymphocytic choriomeningitis virus (LCMV) inhibits transcription and RNA replication of an LCMV S-segment minigenome. | journal=J Virol | year= 2001 | volume= 75 | issue= 19 | pages= 9415-26 | pmid=11533204 | doi=10.1128/JVI.75.19.9415-9426.2001 | pmc=PMC114509 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=11533204 }} </ref><ref name="pmid9281522">{{cite journal| author=Djavani M, Lukashevich IS, Sanchez A, Nichol ST, Salvato MS| title=Completion of the Lassa fever virus sequence and identification of a RING finger open reading frame at the L RNA 5' End. | journal=Virology | year= 1997 | volume= 235 | issue= 2 | pages= 414-8 | pmid=9281522 | doi=10.1006/viro.1997.8722 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=9281522 }} </ref>
* Viral [[RNA]] is unpacked, and [[replication]] and [[transcription]] initiate in the [[cytoplasm]].<ref name="pmid18182084">{{cite journal| author=Rojek JM, Kunz S| title=Cell entry by human pathogenic arenaviruses. | journal=Cell Microbiol | year= 2008 | volume= 10 | issue= 4 | pages= 828-35 | pmid=18182084 | doi=10.1111/j.1462-5822.2007.01113.x | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=18182084 }} </ref> As the [[replication]] starts, both S and L [[RNA]] genomes synthesize the antigenomic S and L [[RNAs]], and from the antigenomic [[RNA]]s, genomic S and L [[RNA]] are synthesized. Both genomic and antigenomic RNAs are needed for [[transcription]] and [[translation]]. S [[RNA]] encodes [[GP]] and [[NP]] (viral [[nucleocapsid protein]]) [[proteins]], and L [[RNA]] encodes Z and L [[proteins]]. L [[protein]] most likely represents the viral RNA-dependent [[RNA polymerase]].<ref name="pmid12615304">{{cite journal| author=Drosten C, Kümmerer BM, Schmitz H, Günther S| title=Molecular diagnostics of [[viral hemorrhagic fevers]]. | journal=Antiviral Res | year= 2003 | volume= 57 | issue= 1-2 | pages= 61-87 | pmid=12615304 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=12615304 }} </ref>.
**The small segment encodes the [[nucleoprotein]] (NP) and the surface [[glycoprotein precursor]] ([[GP]] or viral spike). The GP protein is cleaved into the [[envelope]] [[glycoproteins]], [[GP1]] and [[GP2]], that bind to the alpha-dystroglycan [[receptor]] and mediate [[host]] cell entry<ref name="pmid11119613">{{cite journal| author=Smelt SC, Borrow P, Kunz S, Cao W, Tishon A, Lewicki H et al.| title=Differences in affinity of binding of lymphocytic choriomeningitis virus strains to the cellular receptor alpha-dystroglycan correlate with viral tropism and disease kinetics. | journal=J Virol | year= 2001 | volume= 75 | issue= 1 | pages= 448-57 | pmid=11119613 | doi=10.1128/JVI.75.1.448-457.2001 | pmc=PMC113937 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=11119613 }} </ref>
* When the [[cell]] is infected by the [[virus]], [[L polymerase]] is associated with the [[viral RNP]] and initiates the [[transcription]] of the [[genomic RNA]]. The 5’ and 3’ terminal 19 nt viral [[promoter]] regions of both [[RNA]] segments are necessary for recognition and binding of the [[viral polymerase]]. The primary [[transcription]] first transcribes [[mRNAs]] from the genomic S and L [[RNAs]], which code NP and L [[proteins]], respectively. [[Transcription]] terminates at the [[stem-loop]] (SL) structure within the intergenomic region. [[Arenaviruses]] use a cap snatching strategy to gain the cap structures from the cellular [[mRNAs]], and it is mediated by the [[endonuclease]] activity of the [[L polymerase]] and the cap binding activity of NP. [[Antigenomic RNA]] transcribes viral genes GPC and Z, encoded in genomic orientation, from S and L segments respectively. The [[antigenomic RNA]] also serves as the template for the replication.<ref name="pmid23202452">{{cite journal| author=Yun NE, Walker DH| title=Pathogenesis of Lassa fever. | journal=Viruses | year= 2012 | volume= 4 | issue= 10 | pages= 2031-48 | pmid=23202452 | doi=10.3390/v4102031 | pmc=PMC3497040 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=23202452 }} </ref> After [[translation]] of GPC, it is posttranslationally modified in the [[endoplasmic reticulum]].
*[[Nucleotide]] studies of the [[genome]] have shown that Lassa has four lineages: Three in Nigeria and a fourth in Guinea, Liberia, and Sierra Leone. The Nigerian strains are thought to be ancestral to the others.<ref name="pmid10888638">{{cite journal| author=Bowen MD, Rollin PE, Ksiazek TG, Hustad HL, Bausch DG, Demby AH et al.| title=Genetic diversity among Lassa virus strains. | journal=J Virol | year= 2000 | volume= 74 | issue= 15 | pages= 6992-7004 | pmid=10888638 | doi= | pmc=PMC112216 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10888638 }} </ref>.
* GPC is cleaved into [[GP1]] and [[GP2]] at the later stage of the secretory pathway. It is reported the cellular [[protease]] [[SKI-1]]/[[S1P]] was responsible for the [[cleavage]]. Cleaved [[glycoproteins]] are incorporated into the [[virion]] envelope when the [[virus]] buds and release from the [[cell membrane]].<ref name="pmid12615304">{{cite journal| author=Drosten C, Kümmerer BM, Schmitz H, Günther S| title=Molecular diagnostics of viral hemorrhagic fevers. | journal=Antiviral Res | year= 2003 | volume= 57 | issue= 1-2 | pages= 61-87 | pmid=12615304 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=12615304 }} </ref>


==Natural Reservoir==
==Natural Reservoir==
* The [[reservoir]], or [[host]], of Lassa virus is a [[rodent]] known as the "multimammate rat" (Mastomys natalensis). Mastomys natalensis is commonly known as the “multimammate rat” due to the female’s multiple and prominent mammary glands. Once infected, this rodent is able to [[excrete]] [[virus]] in [[urine]] for an extended time period, maybe for the rest of its life. Mastomys rodents breed frequently, produce large numbers of offspring, and are numerous in the savannas and forests of west, central, and east Africa. In addition, Mastomys readily colonize human homes and areas where food is stored. All of these factors contribute to the relatively efficient spread of Lassa virus from [[infected]] [[rodents]] to [[humans]].
*The most common natural [[reservoir]] of Lassa virus is the [[rodent]], Mastomys natalensis. Mastomys natalensis is commonly known as the “multimammate rat” due to the female’s multiple and prominent mammary glands.  
*The mastomys rodents are abundant in the Savannas and forests of West, Central, and East Africa.
 
*Once infected, the rodent is able to [[excrete]] the [[virus]] in the [[urine]] for an extended time period. Mastomys rodents breed frequently, produce large numbers of offspring, and commonly inhabit human homes with food storage. All of these factors contribute to the relatively efficient spread of Lassa virus from [[infected]] [[rodents]] to [[humans]].
 
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The images below display key features of the Lassa virus.
The images below display key features of the Lassa virus.
<gallery>
<gallery>
Image:Micro lassa 01.jpg|This transmission electron micrograph (TEM) depicted numbers of Lassa virus virions adjacent to some cell debris. Source: CDC microbiologist C. S. Goldsmith, P. Rollin, M. Bowen.<SMALL><SMALL>''[http://phil.cdc.gov/phil/details.asp  Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.]''<ref name="PHIL">{{Cite web | title = Public Health Image Library (PHIL), Centers for Disease Control and Prevention | url = http://phil.cdc.gov/phil/details.asp/}}</ref></SMALL></SMALL>
Image:Micro lassa 01.jpg|This transmission electron micrograph (TEM) demonstrates Lassa virus virions adjacent to host cell debris.<SMALL><SMALL>''[http://phil.cdc.gov/phil/details.asp  Retrieved from the Public Health Image Library (PHIL), Centers for Disease Control and Prevention.]''<ref name="PHIL">{{Cite web | title = Public Health Image Library (PHIL), Centers for Disease Control and Prevention | url = http://phil.cdc.gov/phil/details.asp/}}</ref></SMALL></SMALL>
Image:Lassa virions.jpg|This highly magnified transmission electron micrograph (TEM) depicted some of the ultrastructural details of three Lassa virus virions.<SMALL><SMALL>''[http://phil.cdc.gov/phil/details.asp  Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.]''<ref name="PHIL">{{Cite web | title = Public Health Image Library (PHIL), Centers for Disease Control and Prevention | url = http://phil.cdc.gov/phil/details.asp}}</ref></SMALL></SMALL>
Image:Lassa virions.jpg|This highly magnified transmission electron micrograph (TEM) demonstrates ultrastructural details of 3 Lassa virus virions.<SMALL><SMALL>''[http://phil.cdc.gov/phil/details.asp  Retrieved from the Public Health Image Library (PHIL), Centers for Disease Control and Prevention.]''<ref name="PHIL">{{Cite web | title = Public Health Image Library (PHIL), Centers for Disease Control and Prevention | url = http://phil.cdc.gov/phil/details.asp}}</ref></SMALL></SMALL>
Image:Arenavirus01.jpeg|This transmission electron micrograph depicted eight virions (viral particles) of a newly-discovered virus, which was determined to be a member of the genus, Arenavirus. A cause of fatal hemorrhagic fever, it was confirmed that this virus was responsible for causing illness in five South Africans, four of whom died having succumbed to its devastating effects. Source: CDC microbiologist Charles Humphrey<SMALL><SMALL>''[http://phil.cdc.gov/phil/details.asp  Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.]''<ref name="PHIL">{{Cite web | title = Public Health Image Library (PHIL), Centers for Disease Control and Prevention | url = http://phil.cdc.gov/phil/details.asp}}</ref></SMALL></SMALL></gallery>
Image:Arenavirus01.jpeg|This transmission electron micrograph depicted eight virions (viral particles) of an Arenavirus.<SMALL><SMALL>''[http://phil.cdc.gov/phil/details.asp  Retrieved from the Public Health Image Library (PHIL), Centers for Disease Control and Prevention.]''<ref name="PHIL">{{Cite web | title = Public Health Image Library (PHIL), Centers for Disease Control and Prevention | url = http://phil.cdc.gov/phil/details.asp}}</ref></SMALL></SMALL></gallery>
==References==
==References==
{{Reflist|2}}
{{Reflist|2}}

Revision as of 15:50, 9 June 2015

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ammu Susheela, M.D. [2]

Synonyms and keywords: Lassa hemorrhagic fever; LHF

Overview

Lassa fever is caused by the Lassa virus, a member of the Arenaviridae family. It is an enveloped, single-stranded, bisegmented RNA virus. Mastomysrodents shed the virus in urine and droppings. The direct contact with these materials or ingestion or inhalation, can lead to infection. Lassa virus enters the cell by the receptor-mediated endocytosis and undergoes very rapid replication and manifest the disease.

Causes

Taxonomy

Biology

  • Lassa virus belongs to Arenaviridae [2].
  • The Arenaviridae are a family of viruses whose members are generally associated with rodent-transmitted diseases in humans. Each virus usually is associated with a particular rodent host species in which it is maintained.

Structure


Genome

  • Lassa virus genome is contained in two RNA segments, each of which encodes 2 viral proteins (total 4 viral proteins)[3][4]
  • Nucleotide studies of the genome have shown that Lassa has four lineages: Three in Nigeria and a fourth in Guinea, Liberia, and Sierra Leone. The Nigerian strains are thought to be ancestral to the others.[8].

Natural Reservoir

  • The most common natural reservoir of Lassa virus is the rodent, Mastomys natalensis. Mastomys natalensis is commonly known as the “multimammate rat” due to the female’s multiple and prominent mammary glands.
  • The mastomys rodents are abundant in the Savannas and forests of West, Central, and East Africa.
  • Once infected, the rodent is able to excrete the virus in the urine for an extended time period. Mastomys rodents breed frequently, produce large numbers of offspring, and commonly inhabit human homes with food storage. All of these factors contribute to the relatively efficient spread of Lassa virus from infected rodents to humans.
Mastomys natalensis or the natal multimammate mouse.[9]
Mastomys natalensis is commonly known as the “multimammate rat” due to the female’s multiple and prominent mammary glands.[9]
  • Mastomysrodents shed the virus in urine and droppings and direct contact with these materials, through touching soiled objects, eating contaminated food, or exposure to open cuts or sores, can lead to infection. Because Mastomys rodents often live in and around homes and scavenge on leftover human food items or poorly stored food, direct contact transmission is common. Mastomys rodents are sometimes consumed as a food source and infection may occur when rodents are caught and prepared. Contact with the virus may also occur when a person inhales tiny particles in the air contaminated with infected rodent excretions.

Gallery

The images below display key features of the Lassa virus.

References

  1. ↑ "Taxonomy browser (Lassavirus)".
  2. ↑ "The Centers for Disease Control and Prevention".
  3. ↑ "Genome:The autobiography of a species in 23 chapters". Nat Genet. 24 (1): 21. 2000. doi:10.1038/71638. PMID 10615121.
  4. ↑ Moshkoff DA, Salvato MS, Lukashevich IS (2007). "Molecular characterization of a reassortant virus derived from Lassa and Mopeia viruses". Virus Genes. 34 (2): 169–76. doi:10.1007/s11262-006-0050-3. PMC 1892610. PMID 17143722.
  5. ↑ Cornu TI, de la Torre JC (2001). "RING finger Z protein of lymphocytic choriomeningitis virus (LCMV) inhibits transcription and RNA replication of an LCMV S-segment minigenome". J Virol. 75 (19): 9415–26. doi:10.1128/JVI.75.19.9415-9426.2001. PMC 114509. PMID 11533204.
  6. ↑ Djavani M, Lukashevich IS, Sanchez A, Nichol ST, Salvato MS (1997). "Completion of the Lassa fever virus sequence and identification of a RING finger open reading frame at the L RNA 5' End". Virology. 235 (2): 414–8. doi:10.1006/viro.1997.8722. PMID 9281522.
  7. ↑ Smelt SC, Borrow P, Kunz S, Cao W, Tishon A, Lewicki H; et al. (2001). "Differences in affinity of binding of lymphocytic choriomeningitis virus strains to the cellular receptor alpha-dystroglycan correlate with viral tropism and disease kinetics". J Virol. 75 (1): 448–57. doi:10.1128/JVI.75.1.448-457.2001. PMC 113937. PMID 11119613.
  8. ↑ Bowen MD, Rollin PE, Ksiazek TG, Hustad HL, Bausch DG, Demby AH; et al. (2000). "Genetic diversity among Lassa virus strains". J Virol. 74 (15): 6992–7004. PMC 112216. PMID 10888638.
  9. ↑ 9.0 9.1 "Wikipedia Natal multimammate mouse".
  10. ↑ 10.0 10.1 10.2 "Public Health Image Library (PHIL), Centers for Disease Control and Prevention".


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