Hemorrhagic fevers: few clues after 25 years

Area of Science:

• Virology
• Epidemiology
• Immunology

Background:

• Ebola virus (Filoviridae) is a significant public health concern.
• Previous serological studies indicated a high prevalence of Ebola antibodies in Kenya.
• Clinical disease and virus isolation were previously absent in Kenya.

Purpose of the Study:

• To investigate the prevalence and potential sources of Ebola virus antibodies in western Kenya.
• To evaluate the specificity of antibody detection methods used in previous studies.
• To determine if non-human virulent strains of Filoviridae circulate in Kenya.

Main Methods:

• A field study was conducted in 7 hospitals in western Kenya from 1986-1987.
• Samples were collected from 1109 patients with fever/bleeding, 155 contacts, and 916 individuals in suspect areas.
• Indirect immunofluorescent assay (IFA) was used for antibody detection; viral cultures were performed; confirmatory testing with ELISA and IFA was done in 1995.

Main Results:

• 160/1109 (14.4%), 44/155 (28.4%), and 80/916 (8.7%) individuals tested positive for antibodies, primarily to Ebola.
• No virus was isolated from 676 viral cultures.
• IFA testing showed significant cross-reactivity with Borrelia burgdorferi, Plasmodium falciparum, and Salmonella typhi antibodies; results varied between laboratories.

Conclusions:

• The high prevalence of antibodies in Kenya is likely due to cross-reactivity and non-specific testing, not active Ebola virus infection.
• Non-human virulent strains of Filoviridae, including Ebola virus, may circulate in Kenya.
• Further investigation with highly specific diagnostic methods is warranted to confirm the presence of Filoviridae.