Evidence of human exposure to tick-borne viruses based on viromes of ticks and presence of specific antibodies among patients in Hainan Island, southern China

Hainan Island, located in the South China Sea, is known as an area with diseases related to Rickettsia spp. or spirochete infection; however, the potential threat there from infection with tick-borne viruses (TBVs) remains obscure. In the present study, the dominant tick species, including Rhipicephalus sanguineus and Rhipicephalus microplus, were collected in Hainan Island, and tick viromes were investigated by metagenomic sequencing. In total, 27 viral species were identified belonging to the families Orthomyxoviridae, Flaviviridae, Nairoviridae, Phenuiviridae, Totiviridae, Chuviridae, Rhabdoviridae, and Parvoviridae, amongst which one novel virus and 13 new strains were discovered. Subsequently, individual ticks were screened for seven TBVs, Huanggang Rhabd tick virus 1 (HRTV1), Lihan tick virus (LHTV), Mivirus (MIV), Guangdong tick quaranjavirus (GTQV), Wenchang Ephemerovirus (WEPMV), Jingmen tick virus (JMTV), and brown dog tick phlebovirus (BDPTV), resulting in high prevalence rates of 16.97%, 9.59%, 10.33%, 7.38%, 7.01%, 6.27%, and 3.69%, respectively. While co-infection with multiple viruses was more frequent in R. sanguineus, R. microplus ticks generally had higher viral loads. Four febrile patients showed antibody responses to three TBVs, one each to LHTV and JMTV, and two to GTQV; the patient with antibodies to JMTV also showed neutralizing activity against this virus. This study promoted our understanding of the diversity and complexity of the TBV community in Hainan Island. The results provide serological evidence that human exposure to TBVs like JMTV may have occurred in Hainan, raising concern about potential risks from TBVs and the need to perform further surveys of TBVs among ticks, animals and humans.