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The arenavirus
Lassa causes a severe
illness called Lassa fever.
Lassa fever was first recognized in
herdsmen’s village in Nigeria in 1969.
Lassa fever is
known to be endemic in Guinea (Conakry), Liberia, Sierra Leone and
parts of Nigeria, but probably exists in other West African countries
as well.
Lassa fever has been seldom investigated outside of a few hyperendemic regions, where the described
epidemiology may differ from that in areas of low or moderate
incidence of disease.
Lassa fever is a
serious, highly infectious, viral, hemorrhagic disease characterized
by high fever, prostration, generalized hemorrhages, abdominal pain,
vomiting, diarrhea, severe pharyngitis, dyspnea, serous effusions,
facial edema, and shock.
It is fatal in almost half the cases.
Some studies indicate that 300 000 to 500 000 cases of Lassa fever and
5000 deaths occur yearly across West Africa.
The lassa virus emerged suddenly and may be a virulent mutant of the
lymphocytic choriomeningitis virus.
The lassa virus appears to have a
natural cycle of transmission in rodents and has been isolated
repeatedly from a rat, Mastomys natalensis (commonly
known as the “multimammate rat”). Mastomys infected with Lassa virus
can shed the virus in their excreta (urine and faeces).
According to a study,
Mastomys
natalensis, the reservoir of Lassa virus, constituted 50%-60% of the
rodents captured in houses but only 10%-20% of those captured in
surrounding agriculture and bush areas, a finding suggesting that
houses are the most-important location for transmission of Lassa
virus.
Lassa fever is
difficult to distinguish from many other diseases which cause fever,
including
malaria
,
shigellosis
,
typhoid fever
,
yellow fever and other viral
haemorrhagic fevers.
Visit:
Ebola Virus Infection
;
Marburg Virus Disease
.
The disease spreads from patients to
uninfected persons in households and hospitals.
Anti-Lassa
antibodies are detected by indirect immunofluorescence assay (IFA) or
by enzyme-immunoassay (ELISA).
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