Lassa Fever

Fig. 1 Arenavirus

Introduction
            Lassa Fever is an acute viral illness found in western Africa.  The first case occurred in 1969 in the town of Lassa located in Nigeria.  In endemic areas the virus is a significant cause of morbidity and mortality.  Over 80% of the infections in these areas are subclinical, and only cause 5,000 deaths per year resulting in a mortality rate of only 1%.  However, in pregnant women Lassa Fever is far more detrimental.  This virus results in a 30% fatality rate in pregnant women and is 95% lethal to a fetus in the third trimester.  The reservoir for the virus is the multimammate rat.  Since the rat sheds the virus in its urine and fecal material, this is the source of the virus' primary transmission to humans. Therefore the virus is spread by touching objects, eating contaminated food, or having open sores infected with this material.  The virus can also be inhaled as tiny particles of air can be contaminated with rodent excretions.  Once in humans, the virus can also spread from person to person.  Contamination occurs when an unaffected individual comes in contact with blood, tissue, secretion, or excretions of an individual with Lassa Fever.

Fig. 2 multimammate rat

Incubation Period
            -1- 3 weeks
Symptoms
            -Because symptoms are varied and nonspecific, diagnosis is difficult.
            -Include fever, back pain, sore throat, cough, abdominal pain, vomiting, and facial swelling
            -Neurological symptoms include tremors and encephalitis
            -Permanent hearing loss occurs in one third of all cases
            -Death occurs before appearance of IgM
Diagnosis
            -Most often ELISA testing is used to detect IgM, IgG, and the Lassa antigen
            -Can also culture the virus in 7-10 days.
Treatment
            -Ribavarin- an anti viral drug has been shown to be effective when given early in the course of
                the illness
            -Supportive care is also very important.  Must maintain the appropriate fluid and electrolyte
                balance, oxygenation and blood pressure, and treatment of secondary infections.
Prevention
            -There may soon be a possible vaccine available as vaccinia has
                expressed a Lassa virus structural protein.
            -Reduce rodent populations
            -Keep food in rodent proof containers
            -In a hospital setting: wear protective clothing, isolate infected
                patients, and sterilize equipement properly.

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References:
Centers for Disease Control
 World Health Organization