Confirmation of Xi'an as an epidemic zone of multiple hantavirus types by neutrolizing test

Objective To analyze the status of Hantaan virus (HTNV) and Seoul virus (SEOV) infections in Xi'an area, and to determine the natural foci of HFRS in Xi'an, Shaanxi province. Methods The seasonal characteristics of HFRS in Xi'an were analyzed according to the reported data. Hantavirus RNA from lung samples of mice and rats were analyzed and serotyped by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). The microneutralization tests were performed to detect Hantavirus types. and The protective antibodies against hantavirus were tested in the three groups, including HFRS patients, latent infections and vaccine recipients groups. Then a retrospective epidemiological investigation was carried out on the positive persons. Results There were two HFRS incidence peaks every year in Xi'an, the small one was from June to July and the big one was from October to December. Of the lung samples from 642 mice and 1546 rats, 136 were Hantavirus RNA positive, and all of which belongs to Hantaan virus. Of 143 human sera, 123 were anti-hantavirus neutralizing antibody positive, and 20 were negative. Of these positive cases, 92 were diagnosed as infections of hantaan virus (74.80%), 3 were diagnosed as infections of Seoul virus (2.44%), and the remaining 28 cases could not be serotyped (22.76%). Among the three cases of Seoul virus infection, one was HFRS patients, the second was HFRS vaccine recipient, and the third was latent infection. And retrospective survey indicated that all of the three cases were infected locally. Conclusions Laboratory and field investigation data confirmed that Seoul virus infection exists in Xi'an area of Shaanxi province, where should be regarded as an epidemic area of multiple types of HFRS with hantaan virus as the predominant type. Key words: Hantaan virus; Seoul virus; Neutralizing antibody; Xi’an; Endemic area