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Pathology of Lassa Fever

Acute Haemorrhagic Fever caused by Arena Virus - Lassa

Dr Sampurna Roy MD 




The Arenavirus Lassa causes a severe illness called Lassa fever.

Lassa fever was first recognized following the deaths of two nurses in Nigeria in 1969.  

Lassa fever is known to be endemic in Guinea, 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.

In severe cases there is bleeding from nose, mouth, vagina and gastrointestinal tract.

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 hemorrhagic 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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Further reading:

Reverse ELISA for IgG and IgM antibodies to detect Lassa virus infections in Africa.

Pathogenesis of Lassa Fever

Lassa fever.

Prevention of lassa Fever in Nigeria.

The pathology of human Lassa fever

Pathophysiology and treatment of Lassa fever

Effective vaccine for lassa fever.

Lassa fever in West African sub-region: an overview

A historical look at the first reported cases of Lassa fever

Historical Lassa fever reports and 30-year clinical update.

Development of a new vaccine for the prevention of Lassa fever.

Lassa fever in Guinea: I. Epidemiology of human disease and clinical observations.

Lassa fever in Guinea: II. Distribution and prevalence of Lassa virus infection in small mammals.

Genetic diversity among Lassa virus strains.

A prospective study of the epidemiology and ecology of Lassa fever.



Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)

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