Epidemic characteristics of hemorrhagic fever with renal syndrome in China, 2006–2012

BACKGROUND: Hemorrhagic fever with renal syndrome (HFRS) caused by hantaviruses is a serious public health problem in China. The National Notifiable Disease Surveillance System (NNDSS) was established online by China CDC in 2004 and rodent surveillance sites were adjusted to 40 sites in 22 provinces in 2005. Here we analyzed the surveillance data of both human cases and rodents host during 2006–2012 to examine the epidemic trends of HFRS in recent years in China. METHODS: Records on HFRS human cases and surveillance data of rodents host from 2006 to 2012 were analyzed. Phylogenetic tree based on complete sequence of M segment of 58 virus isolates was constructed and analyzed to make a better understanding of the molecular diversity of hantaviruses in China. RESULTS: During 2006–2012, a total of 77558 HFRS human cases and 866 deaths were reported with the average annual incidence rate of 0.83 cases/100,000 population and case fatality rate of 1.13%. 84.16% of the total cases were clustered in 9 provinces and mainly reported in spring and autumn-winter seasons. HFRS incidence in males was over 3 times higher than in females and farmers still accounted for the largest proportion. The average density of rodents was relatively stable from 2006 to 2012. Apodemus agrarius and Rattus norvegicus were predominant in wild field and residential area, respectively. Both hantaviruses carrying and infection rates in rodents had a rapid increase in 2012. Phylogenetic analysis showed that at least six clades of Hantaan virus and five of Seoul virus were prevalent in China. CONCLUSION: HFRS in China was still a natural focal disease with relatively high morbidity and fatality and its distribution and epidemic trends had also changed. Surveillance measures, together with prevention and control strategies should be improved and strengthened to reduce HFRS infection in China.