To investigate determinants of hemorrhagic fever with renal syndrome (HFRS) in low-lying areas of China, the authors studied Chuigang and Wanggang communities in Anhui Province. These adjacent farming communities have a population of about 100,000. Data were collected from the two communities in 1961-1977 and from Yingshang County in 1983-1995; information covered the incidence of HFRS, amount of precipitation, differences in the water level of the Huai River, density of Apodemus agrarius, autumn crop production, and areas of inundated farmland. Correlation and multiple linear regression analyses were used to estimate the relation between seasonal rainfall, density of mice, occupational factors, and occurrence of the disease. Associations were observed between the incidence of HFRS and the amount of precipitation, the water level of the Huai River, and the areas of inundated farmland in Chuigang community. The smaller the water-level difference, the less farmland was inundated and the higher the incidence of HFRS. In Wanggang community, the density of A. agrarius (r1=0.63, p=0.02), the water-level difference in the Huai River (r2=-0.81, p=0.007), and crop production (r3=0.96, p=0.005) were correlated with the incidence of HFRS. The regression analyses based on Wanggang community suggested that these indexes could be used as predictive variables, and the results from the model were well calibrated with the actual incidence of HFRS in that community (R2=0.88, p < 0.01) and Yingshang County (R2=0.91, p < 0.01).
PIP: The determinants of hemorrhagic fever with renal syndrome (HFRS) in low-lying areas of China were investigated in studies conducted in Chuigang and Wanggang (Anhui Province) in 1961-77 and in Yingshang County in 1983-95--communities with consistently high incidence rates of HFRS. The incidence of HFRS was assessed in relation to amount of precipitation, differences in the water level of the Huai River, density of Apodemus agrarius mice, autumn crop production, and areas of inundated farmland. An inverse association was found between the amount of rainfall, the Huai River's level, areas of inundated farmland (an index reflecting people's contact with rodents), and HFRS incidence. Results from estimation models based on these three predictive factors were well calibrated with the actual incidence of HFRS. In years with less-than-normal rainfall, more farmland is available for planting, creating a favorable microenvironment for mice and increases in their numbers. The local density of mice was 10% in 1961-62, when there was a relatively low amount of precipitation, compared with 2% in 1963-64, when precipitation was above average.