Surveillance of hemorrhagic fever with renal syndrome in China, 2009

Objective To understand the epidemiological characteristics of hemorrhagic fever with renal syndrome (HFRS) in mainland China in 2009, Methods Descriptive epidemiological analysis was conducted on the surveillance data of HFRS collected from national disease reporting information system and 40 HFRS surveillance sites in China in 2009. Results A total of 8745 HFRS cases were reported in China in 2009, a decline of 3.15% compared with 2008, the incidence was 0.66/lakh. Totally 104 cases died, the case fatality rate was 1.19%. The disease remained to occur mainly in northeastern and eastern China, and the first 7 provinces reporting high incidence of HFRS were Heilongjiang, Shaanxi, Shandong, Jilin, Liaoning, Hunan, Zhejiang and Jiangxi. Two incidence peaks were observed in spring and autumn-winter season, but the incidence in autumn-winter season was higher than that in spring. The male to female ratio of the cases was 3.37 ∶ 1. The cases were mainly young males and the mostly affected population was farmers. Up to 907 cases were reported in national surveillance areas, accounting for 10.37% of the total. The incidence trend in surveillance areas was consistent with national incidence trend. Compared with 2008, the overall rat density and rats virus carriage didnt changed obviously, the decline of rats virus carriage rate was found in most areas where the rate had been high, but the local increase was found in these areas. Apodemus agrarius was the predominant species in wild field and Rattus norvegicus was the predominant species in residential area. The 2 species are still the main animal hosts and infectious sources of HFRS in China. Conclusion The reported incidence of HERS in China declined steadily in recent years, but the rat density and rats virus carriage rate remained to be high in some surveillance areas, the risk of HFRS epidemic still exist. It is necessary to strengthen the rodent control and immunization of high risk population in high-endemic areas.