Hemorrhagic fever virus infections in an isolated rainforest area of central Liberia. Limitations of the indirect immunofluorescence slide test for antibody screening in Africa.

Serum samples from 119 healthy individuals and 106 epilepsy patients inhabiting Grand Bassa County, Liberia, were tested for antibodies to hemorrhagic fever viruses (HFV) by indirect immunofluorescence. E6 Vero cells infected with Lassa fever virus (LAS), Rift Valley Fever virus (RVF), Congo Hemorrhagic Fever virus (CON), Marburg virus (MBG) and the Ebola (EBO) virus strains Mayinga (May) and Boniface (Bon) were used as antigen. To obtain reproducible and specific test results sera had to be absorbed extensively with uninfected E6 Vero cells, tested for reactivity to both virus infected and uninfected E6 Vero cells and read "blindly" by two independent observers. Antibodies to EBO were shown to be highly prevalent (13.4%) in the population of this rainforest area, while prevalences of antibodies to LAS (1.3%), RVF (0.4%) and MBG (1.3%) were much lower. No correlation between past HFV infection and post-encephalitic epilepsy or other reported febrile illnesses could be established.