Objective: To characterize the spatial distribution of typhoid and paratyphoid fever (TPF) in Yunnan province, China and to determine the effectiveness of meteorological factors on the epidemics of TPF.
Methods: Data of reported TPF cases in Yunnan province (2001 - 2007) from the China Information System for Diseases Control and Prevention was applied to GIS-based spatial analyses to detect their spatial distribution and clustering of TPF incidence at the county level. Panel data analysis was used to identify the relationships between the TPF incidence and meteorological factors including monthly average temperature, monthly cumulative precipitation and monthly average relative humidity.
Results: During the study period, the average incidence of TPF in Yunnan province was 23.11/100 000, with majority of the TPF cases emerged in summer and autumn. Although widely distributed, two TPF clusters were detected in Yunnan province based on the spatial analysis: one area around Yuxi city with the average annual incidence as 207.45/100 000 and another at the junctions of Yunnan province with Burma and Laos. Based on results from panel data analysis, the incidence of TFP was shown to be associated with meteorological factors such as temperature, precipitation, relative humidity and one month lag of temperature increase [10°C increase in the monthly average temperature: IRR = 1.30 (95%CI: 1.24 - 1.36); 10% increase in monthly average relative humidity: IRR = 1.07 (95%CI: 1.05 - 1.09); 100 mm rise in monthly cumulative precipitation: IRR = 1.02 (95%CI: 1.00 - 1.03); and 10°C average temperature increase, the last month: IRR = 1.73 (95%CI: 1.64 - 1.82)].
Conclusion: Areas with high TPF incidence were detected in this study, which indicated the key areas for TPF control in Yunnan province. Meteorological factors such as temperature, precipitation and humidity played a role in the incidence of TPF.