Haemorrhagic fever virus activity in equatorial Africa: distribution and prevalence of filovirus reactive antibody in the Central African Republic.

Seroepidemiological surveys were conducted to determine the frequency and distribution of haemorrhagic fever virus (HFV) activity in the Central African Republic. Human serum specimens (4295) were collected from 5 ecologically distinct zones. Serological evidence of HFV activity was found in all the zones. The filovirus antibody prevalence (24.4%, 1051/4295) was greater than the combined prevalence for Lassa virus, Rift Valley fever virus and Crimean-Congo HFV antibody (1.1%, 45/4295; P < 0.01). Evidence of filovirus activity was found in all zones: 21.3% (914/4295) of the population were seropositive for Ebola virus antibody while only 3.2% (137/4295) were seroreactive with Marburg viral antigens. Age and sex were important host-related factors influencing filovirus activity, particularly in dry grassland and moist forest communities. These communities shared many factors, but differences, such as agricultural practices and ethnic backgrounds, may also affect the risk of infection. Filovirus infections appear to occur without apparent disease. Continued investigations are needed to evaluate the true pathogenicity of the African filoviruses and the likelihood that unidentified serologically cross-reacting and non-pathogenic members of the filovirus family are active in equatorial Africa.