| Objective: 1. To better understand the incidence characteristic of bacillary dysentery in Hefei, and identify the area with the highest incidence; 2. Use the time-series analysis method to investigate the relationship between bacillary dysentery and temperature change, and explore potential vulnerable people and area;(3) Quantify whether long-term high temperatures could affect bacillary dysentery, so as to provide theoretical foundation for setting up targeting preventive measures.Methods: 1. Daily morbidity data on bacillary dysentery, including the name, age, gender, onset date and address during 2006-2012 in Hefei were obtained from Hefei Center for Disease Control and Prevention. We retrieved Hefei daily weather records from 2006 to 2012 including maximum temperature, average temperature, minimum temperature, rainfall and relative humidity from Local Bureau of Meteorology; 2. According the administrative area, Hefei was divided into the urban area and rural area, and Arc GIS was applied to identify the area with highest bacillary dysentery incidence rate; 3. Based on the time-series about bacillary dysentery and various weather variables, we used the distribute lag non-linear model in R software to analyze the association of temperature and bacillary dysentery, and investigate whether temperature has a lag effect; 4. We also assessed the effect of diurnal temperature range(DTR) on bacillary dysentery; 5. Using different heat wave definitions, we analyzed the characteristic of heat wave happened during study period in Hefei, and explored the effect of heat wave, including its intensity and duration on bacillary dysentery.Results: 1. We observed a significant seasonality for bacillary dysentery occurrence during 2006-2012 in Hefei and the peak time is April to October, with 12717 caseshave happened, accounting for 82.6 percent of total cases. During the peak time, 7109 male cases occurred(56%), and the number of children and adults were greater than the elderly, with a ratio of 5:5:1. Additionally, the number of urban people was double than that of rural people. The average value for mean temperature and DTR were 24.6°C(range: 10.6°C~34.0°C) and 8.0°C(range: 1.2°C~18.1°C); 2. There was a non-linear link between bacillary dysentery and temperature, and temperature effect appeared to be acute. Temperature rise could significantly increase the risk of bacillary dysentery, with a 1°C increase in temperature being associated with 1.0% increase of bacillary dysentery(RR:1.010,95%CI:1.005~1.016). Meanwhile, the high temperature could also lead to 8.8% increase of bacillary dysentery. After stratifying by age and area, we found that children, adults and urban residents were more sensitive to the temperature increase; 3. The increase of DTR could significantly increase the number of bacillary dysentery case, and the RR for the extreme high DTR was 1.075(95%CI:1.023~1.130). Also, children, the elderly and urban residents were found to be more vulnerable to the DTR; 4. Based on various heat wave definitions, we noted that heat wave has occurred frequently in Hefei, with the number ranging from 1 to 89. However, heat wave, inclusion of the intensity and duration has no adverse effect on bacillary dysentery.Conclusions: The urban area of Hefei was hardest hit spot of bacillary dysentery, and temperature was a major contributor to the occurrence of bacillary dysentery. Temperature increase and rapid temperature variation within one day could significantly increase the risk of bacillary dysentery. Under the global warming trend, children and urban residents will be at greater risk of being infected by bacillary dysentery. |
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