Objective To investigate the epidemiological features of hemorrhagic fever with renal syndrome (HFRS), rodent distribution, and the molecular evolutionary characteristics of hantavirus (HV) carried by rodents in Chuxiong, Yunnan province, China. Methods The data of HFRS cases were collected for descriptive epidemiological analysis. The night trapping method was used for rodents, and the composition ratio and density of rodents were calculated. Rodent lungs were collected to detect HV nucleic acid by RT-PCR and to sequence partial fragments of the L gene. Homology and phylogenetic tree analyses were performed using the bioinformatics software ClastalX 1.83 and MEGA 6.0. Results A total of 186 cases of HFRS were reported in Chuxiong from 2015 to 2018, with a mean annual incidence of 7.74/100 000. HFRS occurred in 14 townships of Chuxiong and was mainly epidemic in Lucheng and Donggua towns, which had 75.27% (140/186) of the total cases. There was onset of the disease every month throughout the year. The male-to-female ratio was 2.1:1, and the most cases were young adults and farmers. A total of 1 053 rodents involving 3 species were captured in the residential area of Chuxiong from May to October of 2015-2018; Rattus norvegicus, R. tanezumi, and R. sladeni accounted for 97.06%, 1.80%, and 1.14%, respectively; the densities of the three species were 2.57%, 0.05%, and 0.03%, respectively, with the highest density of 3.09% in Lucheng and Donggua towns. RT-PCR showed that HV nucleic acid was positive in 2 (4.00%; CX04-06 and CX07-09) of 50 lung specimens of R. norvegicus captured in 2016. According to the homology analysis of partial L fragment, the virus strains CX04-06 and CX07-09 were 72.34% to 93.52% homologous in nucleotides to 8 Seoul viruses (SEOV), and had the highest homology (92.39% to 93.52%) to the DLR2 strain of Xiangyun county, Yunnan province and L0199 strain of Laos among the 8 strains, but still with significant differences; they had a low homology to Hantaan virus (69.54% to 71.76%) and Puumala virus (51.19% to 54.44%). Phylogenetic analysis exhibited that the CX04-06 and CX07-09 strains had a close relationship with SEOV reference strains from Xiangyun and Laos. Conclusion There is a high incidence of HFRS in Chuxiong. Rattus norvegicus is the dominant species in the indoor environment of residential areas and carries SEOV, and the epidemic strains show regional characteristics. The rise of HFRS epidemic in Chuxiong is closely related to the widespread distribution and increased population density of R. norvegicus.
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