What is Lassa fever

Lassa fever is a disease of the blood, liver and spleen. Lassa fever is a viral haemorrhagic fever.

Statistics on Lassa fever

This illness was first documented in the town of Lassa, Nigeria, in 1969 and is confined to sub-Saharan West Africa (Nigeria, Liberia and Sierra Leone). Only 10-30% of infections are symptomatic.

Risk Factors for Lassa fever

Mastomys natalensis (rat) is the reservoir of the disease. Humans are infected by eating foods contaminated by rat saliva or urine containing the virus. There is also human-to-human spread by body fluids.

Progression of Lassa fever

The disease is insidious in onset and is characterized by fever, myalgia, severe backache, malaise and headache. A transient maculopapular rash may be present. A sore throat, pharyngitis and lymphadenopathy occur in over 50% of patients. In severe cases epistaxis and gastrointestinal bleeding may occur.

How is Lassa fever Diagnosed?

Laboratory abnormalities:

  • FBC: low Hb due to bleeding from GI tract; thrombocytopaenia.
  • Coagulation studies and LFTs may also be abnormal.

Prognosis of Lassa fever

Death occurs in 15-20% of hospitlised patients, usually from irreversible hypovolaemic shock, but most patients recover within a month. If left untreated, the mortality rate approaches 50%.

How is Lassa fever Treated?

Treatment is supportive.

  • Ribavirin can help reduce mortality if given in the first week.

Health care staff should take great care in handling specimens and clinical material from these patients and strict isolation procedures (e.g. flexible-film isolators) should be used.

Lassa fever References

  1. Kumar P, Clark M. Clinical Medicine. Fourth Ed. WB Saunders, 2002.
  2. Murray PR, Rosenthal KS., Kobayashi GS., Pfaller MA., Medical Microbiology 3rd Ed Mosby 1998.