Epidemiology and changes in age distribution of hemorrhagic fever with renal syndrome in Shaanxi, China, from 2004 to 2023.

INTRODUCTION: Hemorrhagic fever with renal syndrome (HFRS) is a serious viral disease in mainland China, and Shaanxi Province is one of the most severely affected areas. In order to reduce HFRS incidence, an inactivated bivalent vaccine against Hantaan virus (HTNV) and Seoul virus (SEOV) infections was developed and used in China since the 1990s. METHODOLOGY: Descriptive epidemiological methods were used to analyze the spatial, temporal, and population distribution of HFRS along with changes in age distribution in Shaanxi Province from January 2004 to December 2023. RESULTS: A total of 34,265 HFRS human cases were reported in Shaanxi Province, including 25,737 males and 8,528 females. HFRS cases were geographically concentrated in the Guanzhong Plain. The local incidence of HFRS fluctuated remarkably over the past 20 years. The primary peak was from October to January. The proportion of HFRS cases in the 15-60 years age group showed a decreasing trend. However, the proportion of HFRS cases among the > 60 years age group increased by 150.94%, rising from 11.68% to 29.31%. CONCLUSIONS: Data from a 20-year surveillance study shows that the proportion of HFRS cases in individuals over 60 years of age has increased significantly, which may potentially be due to vaccine coverage limitations. The results can be used to adjust the prevention and control measures of HFRS and to consider age-expanded vaccination strategies.