Etiology and genetic feature of 3 cases with severe fever with thrombocytopenia syndrome in Zhoushan

Objective To identify the etiology and genetic evolution of 3 doubtful patients with severe fever with thrombocytopenia syndrome (SFTS) in Zhoushan.Methods Nested RT-PCR assay was used to detect the nucleic acids and 3 specific genes (L,M,S) of novel bunyavirus.The amplification products were sequenced,then the sequencing results were compared with sequences published in GenBank.The evolutionary tree and sequence distance table were constructed by DNAStar software.IgG antibody titers of the sera in recovery phase and in acute phase of 3 patients were measured by indirect immunofluorescence assay.Results Three specific gene segments of novel bunyavirus were all detected in the sera in acute phase of 3 patients,and the homology of S gene between sequences of the gene segments and novel bunyavirus published in GenBank was 94.4％-100.0％.The antibody titers in recovery phase were 4 times more than those in acute phase.Conclusions Three clinical suspected cases are confirmed as recent infections with SFTS by etiology identification.The genetic features of novel bunyavirus in Zhoushan are stable. Key words: Bunyaviridae infections;  Severe fever with thrombocytopenia syndrome;  Pathogenic identification;  Genetic evolution analysis