A prospective study of the epidemiology and ecology of Lassa fever

J Infect Dis. 1987 Mar;155(3):437-44. doi: 10.1093/infdis/155.3.437.


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 (chi 2 = 90.2, P less than 10(-6), df = 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.

MeSH terms

  • Adolescent
  • Adult
  • Animals
  • Antibodies, Viral / analysis
  • Child
  • Child, Preschool
  • Disease Reservoirs
  • Female
  • Humans
  • Lassa Fever / epidemiology*
  • Lassa Fever / transmission
  • Lassa Fever / veterinary
  • Lassa virus / immunology
  • Male
  • Middle Aged
  • Muridae / microbiology
  • Prospective Studies
  • Rodent Diseases / epidemiology
  • Sierra Leone


  • Antibodies, Viral