Lassa fever epidemiology and demographics: Difference between revisions

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==Epidemiology and Demographics==
==Epidemiology and Demographics==
===Prevalence===
===Incidence===
The dissemination of the [[infection]] can be assessed by [[prevalence]] of [[antibodies]] to the virus in [[population]]s of:
* Lassa virus infects 100,000-300,000 individuals annually.  However, these figures are inaccurate given that disease surveillance for cases is not routinely performed.
*Sierra Leone  8–52%
*In areas of high endemicity, up to 10%-16% of hospitalized patients with fever are diagnosed with Lassa fever.
*Guinea 4–55%
*Nigeria approx. 21%
[[File:Outbreak Distribution Map Lassa Fever CDC.png|thumb|center|400 px|Outbreak Distribution Map Lassa Fever CDC.png<ref name="CDC">{{Cite web | title = Center for Disease Control and Prevention (CDC) | url = http://www.cdc.gov/vhf/lassa/outbreaks/index.html}}</ref>]]
* A serological survey among patients admitted with a history of [[fever]] and missionaries that had experienced a febrile illness showed that LASV was also present in Ivory Coast, Mali, and Central African Republic<ref name="pmid1085213">{{cite journal| author=Frame JD| title=Surveillance of Lassa fever in missionaries stationed in West Africa. | journal=Bull World Health Organ | year= 1975 | volume= 52 | issue= 4-6 | pages= 593-8 | pmid=1085213 | doi= | pmc=PMC2366625 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=1085213  }} </ref>.
* The notion that LASV was endemic in larger areas of West Africa was further supported by the results of investigation of an imported case of Lassa fever in Germany in 2000.<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> During the incubation period, the index patient traveled through several countries, namely Ghana, Ivory Coast, and Burkina Faso, that were not considered to be endemic at that time<ref name="pmid10998376">{{cite journal| author=Günther S, Emmerich P, Laue T, Kühle O, Asper M, Jung A et al.| title=Imported lassa fever in Germany: molecular characterization of a new lassa virus strain. | journal=Emerg Infect Dis | year= 2000 | volume= 6 | issue= 5 | pages= 466-76 | pmid=10998376 | doi=10.3201/eid0605.000504 | pmc=PMC2627947 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10998376  }} </ref>.
* Later, cases of Lassa fever have been reported from Burkina Faso, Ivory Coast, Ghana, Senegal, Gambia, and Mali<ref name="pmid17848068">{{cite journal| author=Gonzalez JP, Emonet S, de Lamballerie X, Charrel R| title=Arenaviruses. | journal=Curr Top Microbiol Immunol | year= 2007 | volume= 315 | issue=  | pages= 253-88 | pmid=17848068 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=17848068  }} </ref><ref name="pmid20587185">{{cite journal| author=Safronetz D, Lopez JE, Sogoba N, Traore' SF, Raffel SJ, Fischer ER et al.| title=Detection of Lassa virus, Mali. | journal=Emerg Infect Dis | year= 2010 | volume= 16 | issue= 7 | pages= 1123-6 | pmid=20587185 | doi=10.3201/eid1607.100146 | pmc=PMC3321918 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20587185  }} </ref>.


===Incidence===
* According to estimations, LASV is responsible for 100,000-300,000 infections and approximately 5,000 deaths annually.  Unfortunately, such estimates are crude, because [[disease surveillance|surveillance]] for cases of the disease is not uniformly performed. In some areas of Sierra Leone and Liberia, it is known that 10%-16% of people admitted to hospitals have Lassa fever, which indicates the serious impact of the disease on the population of this region.
===Case Fatality Rates===
===Case Fatality Rates===
* The overall case-fatality rate is 1%. Observed case-fatality rate among patients hospitalized with severe cases of Lassa fever is 15%. Lassa fever is also associated with occasional epidemics, during which the case-fatality rate can reach 50%.<ref name=WHO>{{cite web | title = WHO Lassa fever fact sheet | url =http://www.who.int/mediacentre/factsheets/fs179/en/ }}</ref>
* Generally, the overall case-fatality rate is 1-5%.
* [[Nosocomial outbreaks]] are associated with higher mortality rates ranging from 36% to 65%<ref name="pmid4745236">{{cite journal| author=Monath TP, Mertens PE, Patton R, Moser CR, Baum JJ, Pinneo L et al.| title=A hospital epidemic of Lassa fever in Zorzor, Liberia, March-April 1972. | journal=Am J Trop Med Hyg | year= 1973 | volume= 22 | issue= 6 | pages= 773-9 | pmid=4745236 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=4745236  }} </ref>.
* The case fatality rate increases among patients hospitalized for severe infection and may be as high as 15%.
* In areas of Africa where the disease is endemic (that is, constantly present), Lassa fever is a significant cause of [[morbidity]] and [[mortality]]. While Lassa fever is mild or has no observable symptoms in about 80% of people infected with the [[virus]], the remaining 20% have a severe multisystem [[disease]].
* During outbreaks, Lassa fever may be associated with case-fatality rates that reach up to 35-65%.<ref name="pmid4745236">{{cite journal| author=Monath TP, Mertens PE, Patton R, Moser CR, Baum JJ, Pinneo L et al.| title=A hospital epidemic of Lassa fever in Zorzor, Liberia, March-April 1972. | journal=Am J Trop Med Hyg | year= 1973 | volume= 22 | issue= 6 | pages= 773-9 | pmid=4745236 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=4745236  }} </ref>.
* The high degree of seroprevalence of LASV-specific [[antibodies]] in the general population residing in the endemic regions, although highly variable depending on the geographical location (from 1.8% to 55%) [<ref name="pmid3805771">{{cite journal| author=McCormick JB, Webb PA, Krebs JW, Johnson KM, Smith ES| title=A prospective study of the epidemiology and ecology of Lassa fever. | journal=J Infect Dis | year= 1987 | volume= 155 | issue= 3 | pages= 437-44 | pmid=3805771 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=3805771  }} </ref> indicates that most infections are mild or possibly even asymptomatic and do not result in hospitalization. This is also supported by the findings indicating a high incidence of LASV-specific seroconversion, from 5% to 20% of the nonimmune population per year<ref name="pmid3805771">{{cite journal| author=McCormick JB, Webb PA, Krebs JW, Johnson KM, Smith ES| title=A prospective study of the epidemiology and ecology of Lassa fever. | journal=J Infect Dis | year= 1987 | volume= 155 | issue= 3 | pages= 437-44 | pmid=3805771 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=3805771  }} </ref>.
 
===Age===
===Age===
* People of all ages who are exposed to the infection are vulnerable to get infected.
*There is no age predominance for Lassa virus infection.
*However, fetuses are at high-risk of death following infection with Lassa fever.
 
===Gender===
===Gender===
* The death rates are particularly high for women in the third trimester of [[pregnancy]], and for fetuses, about 95% of which die in the [[uterus]] of infected [[pregnant]] mothers.
* There is no gender predominance for Lassa virus infection.
* Women in the third trimester of [[pregnancy]] are considered high-risk for development of Lassa fever-associated complications and death.
===Seasonal Variation===
===Seasonal Variation===
* Studies conducted prior to the end of hostilities suggested that the highest incidence of LF in Sierra Leone occurs during the dry season (November to April).<ref name="pmid3805771">{{cite journal| author=McCormick JB, Webb PA, Krebs JW, Johnson KM, Smith ES| title=A prospective study of the epidemiology and ecology of Lassa fever. | journal=J Infect Dis | year= 1987 | volume= 155 | issue= 3 | pages= 437-44 | pmid=3805771 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=3805771  }} </ref>
* The highest incidence of Lassa fever occurs during the dry months from November to April.<ref name="pmid3805771">{{cite journal| author=McCormick JB, Webb PA, Krebs JW, Johnson KM, Smith ES| title=A prospective study of the epidemiology and ecology of Lassa fever. | journal=J Infect Dis | year= 1987 | volume= 155 | issue= 3 | pages= 437-44 | pmid=3805771 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=3805771  }} </ref>
===Race===
===Race===
* People of all ages who are exposed to the infection are vulnerable to get infected.
* There is no races predominance for Lassa virus infection.
===Developed Countries===
===Developed Countries===
* People hospitalized in United States with imported Lassa fever.<ref name=Historical Lassa Fever Reports and 30-year Clinical Update-The Centers for Disease Control and Prevention articles>{{cite web | title = Historical Lassa Fever Reports and 30-year Clinical Update-The Centers for Disease Control and Prevention articles | url =http://wwwnc.cdc.gov/eid/article/12/5/pdfs/05-0052.pdf }}</ref>
* Individuals hospitalized in United States with imported Lassa fever.<ref name=Historical Lassa Fever Reports and 30-year Clinical Update-The Centers for Disease Control and Prevention articles>{{cite web | title = Historical Lassa Fever Reports and 30-year Clinical Update-The Centers for Disease Control and Prevention articles | url =http://wwwnc.cdc.gov/eid/article/12/5/pdfs/05-0052.pdf }}</ref>
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| align="center" style="background:#4479BA; padding: 5px 5px;"|{{fontcolor|#FFF|'''Year of import'''}}
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===Developing Countries===
===Developing Countries===
* Since its initial discovery, nosocomial outbreaks of Lassa fever have occurred repeatedly in following countires.
* Since its initial discovery, nosocomial outbreaks of Lassa fever have occurred repeatedly in following countires.
:* Sierra Leone: Panguma, Kenema, 1971–83.
Lassa virus is prevalent in countries of West and Central Africa:<ref name="pmid: 5046380">{{cite journal| author=Carey DE, Kemp GE, White HA, Pinneo L, Addy RF, Fom AL et al.| title=Lassa fever. Epidemiological aspects of the 1970 epidemic, Jos, Nigeria. | journal=Trans R Soc Trop Med Hyg | year= 1972 | volume= 66 | issue= 3 | pages= 402-8 | pmid=: 5046380 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=5046380  }} </ref><ref name="pmid1085214">{{cite journal| author=Bowen GS, Tomori O, Wulff H, Casals J, Noonan A, Downs WG| title=Lassa fever in Onitsha, East Central State, Nigeria in 1974. | journal=Bull World Health Organ | year= 1975 | volume= 52 | issue= 4-6 | pages= 599-604 | pmid=1085214 | doi= | pmc=PMC2366632 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=1085214 }} </ref><ref name="pmid6390808">{{cite journal| author=Frame JD, Jahrling PB, Yalley-Ogunro JE, Monson MH| title=Endemic Lassa fever in Liberia. II. Serological and virological findings in hospital patients. | journal=Trans R Soc Trop Med Hyg | year= 1984 | volume= 78 | issue= 5 | pages= 656-60 | pmid=6390808 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=6390808 }} </ref>,<ref name="pmid7580496">{{cite journal| author=Fisher-Hoch SP, Tomori O, Nasidi A, Perez-Oronoz GI, Fakile Y, Hutwagner L et al.| title=Review of cases of nosocomial Lassa fever in Nigeria: the high price of poor medical practice. | journal=BMJ | year= 1995 | volume= 311 | issue= 7009 | pages= 857-9 | pmid=7580496 | doi= | pmc=PMC2550858 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=7580496 }} </ref><ref name="pmid9373625">{{cite journal| author=Bajani MD, Tomori O, Rollin PE, Harry TO, Bukbuk ND, Wilson L et al.| title=A survey for antibodies to Lassa virus among health workers in Nigeria. | journal=Trans R Soc Trop Med Hyg | year= 1997 | volume= 91 | issue= 4 | pages= 379-81 | pmid=9373625 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=9373625 }} </ref><ref name="pmid15056044">{{cite journal| author=Fisher-Hoch SP, McCormick JB| title=Lassa fever vaccine. | journal=Expert Rev Vaccines | year= 2004 | volume= 3 | issue= 2 | pages= 189-97 | pmid=15056044 | doi=10.1586/14760584.3.4.S189 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=15056044 }} </ref><ref name="pmid16355508">{{cite journal| author=Omilabu SA, Badaru SO, Okokhere P, Asogun D, Drosten C, Emmerich P et al.| title=Lassa fever, Nigeria, 2003 and 2004. | journal=Emerg Infect Dis | year= 2005 | volume= 11 | issue= 10 | pages= 1642-4 | pmid=16355508 | doi=10.3201/eid1110.041343 | pmc=PMC3366737 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16355508 }} </ref>  
:* 1997, Liberia: Zorzor, 1972.
*Sierra Leone
:* Phebe 1972, 1977, 1982.
*Guinea
:* Ganta 1977, 1982.
*Nigeria
:* Nigeria: Jos, 1970, 1993.
*Ivory Coast
:* Onitsha, 1974.
*Mali
:* Zonkwa, 1975.
*Benin
:* Vom, 1975–77, Imo, 1989.
*Central African Republic
:*  Lafia, 1993.
*Liberia
:* Irrua, 2004 <ref name="pmid: 5046380">{{cite journal| author=Carey DE, Kemp GE, White HA, Pinneo L, Addy RF, Fom AL et al.| title=Lassa fever. Epidemiological aspects of the 1970 epidemic, Jos, Nigeria. | journal=Trans R Soc Trop Med Hyg | year= 1972 | volume= 66 | issue= 3 | pages= 402-8 | pmid=: 5046380 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=5046380 }} </ref><ref name="pmid1085214">{{cite journal| author=Bowen GS, Tomori O, Wulff H, Casals J, Noonan A, Downs WG| title=Lassa fever in Onitsha, East Central State, Nigeria in 1974. | journal=Bull World Health Organ | year= 1975 | volume= 52 | issue= 4-6 | pages= 599-604 | pmid=1085214 | doi= | pmc=PMC2366632 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=1085214 }} </ref><ref name="pmid6390808">{{cite journal| author=Frame JD, Jahrling PB, Yalley-Ogunro JE, Monson MH| title=Endemic Lassa fever in Liberia. II. Serological and virological findings in hospital patients. | journal=Trans R Soc Trop Med Hyg | year= 1984 | volume= 78 | issue= 5 | pages= 656-60 | pmid=6390808 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=6390808 }} </ref>,<ref name="pmid7580496">{{cite journal| author=Fisher-Hoch SP, Tomori O, Nasidi A, Perez-Oronoz GI, Fakile Y, Hutwagner L et al.| title=Review of cases of nosocomial Lassa fever in Nigeria: the high price of poor medical practice. | journal=BMJ | year= 1995 | volume= 311 | issue= 7009 | pages= 857-9 | pmid=7580496 | doi= | pmc=PMC2550858 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=7580496 }} </ref><ref name="pmid9373625">{{cite journal| author=Bajani MD, Tomori O, Rollin PE, Harry TO, Bukbuk ND, Wilson L et al.| title=A survey for antibodies to Lassa virus among health workers in Nigeria. | journal=Trans R Soc Trop Med Hyg | year= 1997 | volume= 91 | issue= 4 | pages= 379-81 | pmid=9373625 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=9373625 }} </ref><ref name="pmid15056044">{{cite journal| author=Fisher-Hoch SP, McCormick JB| title=Lassa fever vaccine. | journal=Expert Rev Vaccines | year= 2004 | volume= 3 | issue= 2 | pages= 189-97 | pmid=15056044 | doi=10.1586/14760584.3.4.S189 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=15056044 }} </ref><ref name="pmid16355508">{{cite journal| author=Omilabu SA, Badaru SO, Okokhere P, Asogun D, Drosten C, Emmerich P et al.| title=Lassa fever, Nigeria, 2003 and 2004. | journal=Emerg Infect Dis | year= 2005 | volume= 11 | issue= 10 | pages= 1642-4 | pmid=16355508 | doi=10.3201/eid1110.041343 | pmc=PMC3366737 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16355508 }} </ref>  
*Burkina Faso
* In Guinea, some acute but isolated cases were recorded in hospitals and a single rural outbreak was recorded on the Sierra Leone border in 1982–83<ref name="pmid12653127">{{cite journal| author=Bausch DG, Demby AH, Coulibaly M, Kanu J, Goba A, Bah A et al.| title=Lassa fever in Guinea: I. Epidemiology of human disease and clinical observations. | journal=Vector Borne Zoonotic Dis | year= 2001 | volume= 1 | issue= 4 | pages= 269-81 | pmid=12653127 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=12653127 }} </ref>.
*Senegal
* Between these two areas, namely in Côte d'Ivoire, Ghana, Togo and Benin, no outbreak has ever been recorded, though isolated cases show evidence of viral circulation in that area<ref name="pmid17201291">{{cite journal| author=Akoua-Koffi C, Ter Meulen J, Legros D, Akran V, Aïdara M, Nahounou N et al.| title=[Detection of anti-Lassa antibodies in the Western Forest area of the Ivory Coast]. | journal=Med Trop (Mars) | year= 2006 | volume= 66 | issue= 5 | pages= 465-8 | pmid=17201291 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=17201291 }} </ref><ref name="pmid26022445">{{cite journal| author=Borremans B, Vossen R, Becker-Ziaja B, Gryseels S, Hughes N, Van Gestel M et al.| title=Shedding dynamics of Morogoro virus, an African arenavirus closely related to Lassa virus, in its natural reservoir host Mastomys natalensis. | journal=Sci Rep | year= 2015 | volume= 5 | issue=  | pages= 10445 | pmid=26022445 | doi=10.1038/srep10445 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=26022445  }} </ref>. Lassa fever therefore appears to have 2 geographically separate endemic areas: the Mano River region (Guinea, Sierra Leone, Liberia) in the West, and Nigeria in the East.
*Ghana
*Gambia<br>
The map below demonstrates the outbreak distribution of Lassa fever:<ref name="pmid17848068">{{cite journal| author=Gonzalez JP, Emonet S, de Lamballerie X, Charrel R| title=Arenaviruses. | journal=Curr Top Microbiol Immunol | year= 2007 | volume= 315 | issue= | pages= 253-88 | pmid=17848068 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=17848068 }} </ref><ref name="pmid20587185">{{cite journal| author=Safronetz D, Lopez JE, Sogoba N, Traore' SF, Raffel SJ, Fischer ER et al.| title=Detection of Lassa virus, Mali. | journal=Emerg Infect Dis | year= 2010 | volume= 16 | issue= 7 | pages= 1123-6 | pmid=20587185 | doi=10.3201/eid1607.100146 | pmc=PMC3321918 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20587185 }} </ref><ref name="pmid10998376">{{cite journal| author=Günther S, Emmerich P, Laue T, Kühle O, Asper M, Jung A et al.| title=Imported lassa fever in Germany: molecular characterization of a new lassa virus strain. | journal=Emerg Infect Dis | year= 2000 | volume= 6 | issue= 5 | pages= 466-76 | pmid=10998376 | doi=10.3201/eid0605.000504 | pmc=PMC2627947 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10998376 }} </ref>
[[File:Outbreak Distribution Map Lassa Fever CDC.png|thumb|left|400 px|Outbreak Distribution Map Lassa Fever<ref name="CDC">{{Cite web | title = Center for Disease Control and Prevention (CDC) | url = http://www.cdc.gov/vhf/lassa/outbreaks/index.html}}</ref>]]
{|
{|
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| valign=top |
[[File:Journal.pntd.0002748.g004.png|thumb|center|400 px|Geographic distribution of patients presenting to Sierra Leone with LASV antigenemia and anti-LASV IgM serpositivity, 2008–12.<ref name="Lassa Fever in Post-Conflict Sierra Leone">{{Cite web | title = Lassa Fever in Post-Conflict Sierra Leone| url =  http://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0002748}}</ref>]]
[[File:Journal.pntd.0002748.g004.png|thumb|left|400 px|Geographic distribution of patients presenting to Sierra Leone with LASV antigenemia and anti-LASV IgM serpositivity, 2008–12.<ref name="Lassa Fever in Post-Conflict Sierra Leone">{{Cite web | title = Lassa Fever in Post-Conflict Sierra Leone| url =  http://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0002748}}</ref>]]
|style="width: 300px"|
|style="width: 300px"|
| [[File:Nigeria.jpg|thumb|center|400 px|Map of Nigeria showing States where cases of acute abdomen from Lassa fever were reported.<ref name="Lassa Fever in Post-Conflict Sierra Leone">{{Cite web | title = Lassa fever presenting as acute abdomen: a case series| url =  http://www.virologyj.com/content/10/1/123}}</ref>]]
| [[File:Nigeria.jpg|thumb|left|400 px|Map of Nigeria showing States where cases of acute abdomen from Lassa fever were reported.<ref name="Lassa Fever in Post-Conflict Sierra Leone">{{Cite web | title = Lassa fever presenting as acute abdomen: a case series| url =  http://www.virologyj.com/content/10/1/123}}</ref>]]
|}
|}


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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 endemic in parts of West Africa including Sierra Leone, Liberia, Guinea and Nigeria; however, other neighboring countries are also at risk, as the animal vector for Lassa virus, the "multimammate rat" (Mastomys natalensis) is distributed throughout the region. Lassa fever causes 100,000-300,000 infections and approximately 5,000 deaths annually.[1]

Epidemiology and Demographics

Incidence

  • Lassa virus infects 100,000-300,000 individuals annually. However, these figures are inaccurate given that disease surveillance for cases is not routinely performed.
  • In areas of high endemicity, up to 10%-16% of hospitalized patients with fever are diagnosed with Lassa fever.

Case Fatality Rates

  • Generally, the overall case-fatality rate is 1-5%.
  • The case fatality rate increases among patients hospitalized for severe infection and may be as high as 15%.
  • During outbreaks, Lassa fever may be associated with case-fatality rates that reach up to 35-65%.[2].

Age

  • There is no age predominance for Lassa virus infection.
  • However, fetuses are at high-risk of death following infection with Lassa fever.

Gender

  • There is no gender predominance for Lassa virus infection.
  • Women in the third trimester of pregnancy are considered high-risk for development of Lassa fever-associated complications and death.

Seasonal Variation

  • The highest incidence of Lassa fever occurs during the dry months from November to April.[3]

Race

  • There is no races predominance for Lassa virus infection.

Developed Countries

  • Individuals hospitalized in United States with imported Lassa fever.
Year of import Clinical features From To
1969 Fever, malaise, headache, nausea, sore throat, epigastric/right upper quadrant tenderness, pleural effusion, facial/cervical edema, dysphagia, elevated transaminases, cough, dyspnea, pulmonary infiltrates, epiglottal edema, lethargy, nystagmus, lightheadedness, dizziness without vertigo, ataxia, alopecia Nigeria New York
1975 Abdominal pain, diarrhea, fever, headache, myalgia, arthralgia, conjunctival injection, lymphadenopathy, weight loss, pleuritic chest pain, pleural effusion, unilateral deafness Sierra Leone Washington, DC
1976 Abdominal cramps, nausea, vomiting, diarrhea, fatigue, headache, retroorbital pain, neck/back pain, paresthesias, right ear pain, fever, vertigo, syncope, dysmorphopsias, alopecia, weight loss, ecchymoses, insomnia, depression, hypotension, left-sided facial weakness, right-sided Babinski reflex, Weber test lateralized to the left Sierra Leone Washington, DC
1989 Shaking chills, fever, sore throat, myalgia, headache, dysphagia, bloody diarrhea, elevated transaminases, hypotension, adult respiratory distress syndrome, death Nigeria Chicago, IL
2004 Chills, fever, sore throat, diarrhea, back pain, adult respiratory distress syndrome, death Sierra Leone and Liberia Trenton, New Jersy
2015 Fever, sore throat, tiredness, death Liberia New Jersy

As of May, 2015. Data from the Center of Disease Control and Prevention

  • Patients with imported Lassa fever, worldwide except United States, 1969–2004.
Year of import Occupation From To Clinical outcome
1971 Nurse Sierra Leone United Kingdom Survived
1971 Physician Sierra Leone United Kingdom Survived
1972 Nurse Sierra Leone United Kingdom Survived
1974 Physician Nigeria Germany Survived
1975 Physician Nigeria United Kingdom Died
1976 Engineer Nigeria United Kingdom Survived
1980 Aid worker Upen Volta Netherlands Survived
1981 Teacher Nigeria United Kingdom Survived
1982 Diplomat Nigeria United Kingdom Survived
1984 Geologist Sierra Leone United Kingdom Survived
1985 Nurse Sierra Leone United Kingdom Survived
1987 Engineer Sierra Leone/Liberia Israel Survived
1987 Engineer Sierra Leone Japan Survived
1989 Agricultural specialist Nigeria Canada Survived
2000 Student Cotê d'Ivoire/Burkina Faso/Ghana Germany Died
2000 Peace Keeper CSierra Leone United Kingdom Died
2000 Unknown Nigeria Germany Died
2000 Physician Sierra Leone Netherlands Died
2003 Peace Keeper Sierra Leone United Kingdom Survived
2006 - Sierra Leone Germany Survived

As of May, 2015. Data from the Center of Disease Control and Prevention

Developing Countries

  • Since its initial discovery, nosocomial outbreaks of Lassa fever have occurred repeatedly in following countires.

Lassa virus is prevalent in countries of West and Central Africa:[4][5][6],[7][8][9][10]

  • Sierra Leone
  • Guinea
  • Nigeria
  • Ivory Coast
  • Mali
  • Benin
  • Central African Republic
  • Liberia
  • Burkina Faso
  • Senegal
  • Ghana
  • Gambia

The map below demonstrates the outbreak distribution of Lassa fever:[11][12][13]

Outbreak Distribution Map Lassa Fever[1]
Geographic distribution of patients presenting to Sierra Leone with LASV antigenemia and anti-LASV IgM serpositivity, 2008–12.[14]
Map of Nigeria showing States where cases of acute abdomen from Lassa fever were reported.[14]

References

  1. ↑ 1.0 1.1 "The Centers for Disease Control and Prevention facts sheets" (PDF).
  2. ↑ Monath TP, Mertens PE, Patton R, Moser CR, Baum JJ, Pinneo L; et al. (1973). "A hospital epidemic of Lassa fever in Zorzor, Liberia, March-April 1972". Am J Trop Med Hyg. 22 (6): 773–9. PMID 4745236.
  3. ↑ McCormick JB, Webb PA, Krebs JW, Johnson KM, Smith ES (1987). "A prospective study of the epidemiology and ecology of Lassa fever". J Infect Dis. 155 (3): 437–44. PMID 3805771.
  4. ↑ Carey DE, Kemp GE, White HA, Pinneo L, Addy RF, Fom AL; et al. (1972). "Lassa fever. Epidemiological aspects of the 1970 epidemic, Jos, Nigeria". Trans R Soc Trop Med Hyg. 66 (3): 402–8. PMID 5046380 : 5046380 Check |pmid= value (help).
  5. ↑ Bowen GS, Tomori O, Wulff H, Casals J, Noonan A, Downs WG (1975). "Lassa fever in Onitsha, East Central State, Nigeria in 1974". Bull World Health Organ. 52 (4–6): 599–604. PMC 2366632. PMID 1085214.
  6. ↑ Frame JD, Jahrling PB, Yalley-Ogunro JE, Monson MH (1984). "Endemic Lassa fever in Liberia. II. Serological and virological findings in hospital patients". Trans R Soc Trop Med Hyg. 78 (5): 656–60. PMID 6390808.
  7. ↑ Fisher-Hoch SP, Tomori O, Nasidi A, Perez-Oronoz GI, Fakile Y, Hutwagner L; et al. (1995). "Review of cases of nosocomial Lassa fever in Nigeria: the high price of poor medical practice". BMJ. 311 (7009): 857–9. PMC 2550858. PMID 7580496.
  8. ↑ Bajani MD, Tomori O, Rollin PE, Harry TO, Bukbuk ND, Wilson L; et al. (1997). "A survey for antibodies to Lassa virus among health workers in Nigeria". Trans R Soc Trop Med Hyg. 91 (4): 379–81. PMID 9373625.
  9. ↑ Fisher-Hoch SP, McCormick JB (2004). "Lassa fever vaccine". Expert Rev Vaccines. 3 (2): 189–97. doi:10.1586/14760584.3.4.S189. PMID 15056044.
  10. ↑ Omilabu SA, Badaru SO, Okokhere P, Asogun D, Drosten C, Emmerich P; et al. (2005). "Lassa fever, Nigeria, 2003 and 2004". Emerg Infect Dis. 11 (10): 1642–4. doi:10.3201/eid1110.041343. PMC 3366737. PMID 16355508.
  11. ↑ Gonzalez JP, Emonet S, de Lamballerie X, Charrel R (2007). "Arenaviruses". Curr Top Microbiol Immunol. 315: 253–88. PMID 17848068.
  12. ↑ Safronetz D, Lopez JE, Sogoba N, Traore' SF, Raffel SJ, Fischer ER; et al. (2010). "Detection of Lassa virus, Mali". Emerg Infect Dis. 16 (7): 1123–6. doi:10.3201/eid1607.100146. PMC 3321918. PMID 20587185.
  13. ↑ Günther S, Emmerich P, Laue T, Kühle O, Asper M, Jung A; et al. (2000). "Imported lassa fever in Germany: molecular characterization of a new lassa virus strain". Emerg Infect Dis. 6 (5): 466–76. doi:10.3201/eid0605.000504. PMC 2627947. PMID 10998376.
  14. ↑ 14.0 14.1 "Lassa Fever in Post-Conflict Sierra Leone".

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