A Prospective Study of the Epidemiology and Ecology of Lassa Fever

Publisher Website
Google Scholar
Abstract
In studies of Lassa fever in Sierra Leone, the prevalence. of human antibody to Lassa virus ranged from 8% to 52%. 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 (χ2 = 90.2, P < 10−6 , dƒ = 1), a finding suggesting that houses are the most-important location for transmission of Lassa virus. Viral infection of Mastomys from houses ranged from 0% to 80%. The incidence of seroconversions in susceptible persons ranged from 5% to 22% per year; the ratio of illness to infection ranged from 9% to 26%, and the proportion of febrile illness associated with seroconversion was 5%–14%. Eightfold rises in titer of antibody occurred in 1%–18% of the antibody-positive population, a result suggesting reinfection. We estimate the ratio of fatalities to infection to be 1%–2%, a rate lower than estimates based on hospitalized cases. The high incidence of Lassa fever makes it a major problem in West Africa.