Apodemus agrarius is a potential natural host of severe fever with thrombocytopenia syndrome (SFTS)—causing novel bunyavirus

Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne, novel bunyavirus-caused emerging infectious disease. It becomes a threat to public health due to its high fatality rate.To clarify the epidemiological characteristics of SFTS and natural host(s) of SFTS-causing virus (SFTSV) in East China.Serum antibody against SFTSV in 496 healthy villagers was examined by ELISA. SFTSV in acute sera of SFTS cases and lung tissues of house and field mouse/rats were identified using quantitative RT-PCR, cell culture, and sequencing.A total of 22 laboratory-confirmed SFTS cases were diagnosed between 2012 and 2014, of which 5 (22.7%) reported a history of tick-bites. The seroprevalance of SFTSV antibody was 10.5% in healthy villagers. SFTSV genomic RNAs were identified in 2 of 8 Apodemus agrarius but not in Rattus norvegicus (n=40) and Rattus losea (n=4). The 3 segments of SFTSV from 11 SFTS cases and 2 A. agrarius were successfully sequenced. Phylogenetic analyses indicated that at least 3 different SFTSV strains (inland-type, Ningbo-native-type, and their reassortant-type) were present in Ningbo. The 3 segments of the 2 SFTSV isolates from A. agrarius shared great sequence homologies to those isolated from the patients living in nearby villages.The present study indicated that A. agrarius might be a natural host of SFTSV in East China.