Serologic evidence of human exposure to the severe fever with thrombocytopenia syndrome virus and associated viruses in Kenya.

Background: Although the diverse communities of tick-borne viruses (TBVs) have recently been proposed, the threat of infection and exposure to TBVs among humans across Kenya has been poorly understood.

Objective: Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging tick-borne viral agent associated with the epidemic of severe fever with thrombocytopenia syndrome (SFTS) disease in East Asian countries. This study investigated the seroprevalence of SFTSV among humans in Kenya.

Methods: Serum samples were collected from 459 healthy people in Kenya and tested for anti-SFTSV antibodies, which were further confirmed by immunofluorescence assays. Micro neutralization assays were performed to identify neutralising antibodies against SFTSV and SFTSV-related viruses.

Results: A high seroprevalence (162/459, 35.3%) of SFTSV was found in the samples from nine of the ten surveyed counties in Kenya, with higher rates in the eastern plateau forelands, semiarid and arid areas, and coastal areas than in the area aside Rift valley. The seropositive rate was slightly higher in women than in men and was significantly higher in the 55-64 age group. Neutralising activity against SFTSV was detected in four samples, resulting in a rate of 0.9%. No cross-neutralising activity against the SFTSV-related Guertu virus and Heartland virus was detected in the anti-SFTSV positive serum samples.

Conclusion: The results provide serologic evidence of human exposure to SFTSV in Kenya and extend our understanding of SFTSV prevalence from Asia to Africa. The findings suggest an increasing threat of exposure to emerging TBVs and the need to investigate tick viromes in Kenya.