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

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. 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. 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. 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. 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.

尽管近期已有研究提出蜱传病毒（tick-borne viruses, TBVs）存在多样的类群，但肯尼亚全境人群感染或接触蜱传病毒的相关风险仍鲜为人知。严重发热伴血小板减少综合征病毒（Severe fever with thrombocytopenia syndrome virus, SFTSV）是一种新型蜱传病毒，与东亚国家暴发的严重发热伴血小板减少综合征（severe fever with thrombocytopenia syndrome, SFTS）疫情密切相关。本研究针对肯尼亚人群中SFTSV的血清流行率展开了调查。研究人员从肯尼亚459名健康人群中采集血清样本，检测其中的抗SFTSV抗体，并通过免疫荧光试验（immunofluorescence assays）进一步验证检测结果；同时采用微量中和试验（micro neutralization assays），鉴定针对SFTSV及其相关病毒的中和抗体。在所调研的10个县中，有9个县的样本检测出较高的SFTSV血清阳性率（162/459，35.3%）；其中东部高原山前地带、半干旱及干旱地区与沿海地区的阳性率显著高于东非大裂谷周边区域。女性的血清阳性率略高于男性，而55-64岁年龄组的阳性率则显著更高。共在4份样本中检测到针对SFTSV的中和活性，阳性率为0.9%。在抗SFTSV阳性的血清样本中，未检测到针对SFTSV相关的格尔图病毒（Guertu virus）和哈特兰病毒（Heartland virus）的交叉中和活性。本研究结果为肯尼亚人群存在SFTSV暴露提供了血清学证据，并将我们对SFTSV流行情况的认知从亚洲拓展至非洲。该研究结果提示，肯尼亚人群接触新型蜱传病毒的风险正逐渐升高，同时也凸显了对肯尼亚蜱病毒组（tick viromes）展开研究的必要性。