Effect of ambient temperature and its effect modifiers on bacillary dysentery in Jinan, China.

Background: Studies about the modified effect among various meteorological factors on bacillary dysentery (BD) are limited. This study aimed to investigate the effect of ambient temperature and its effect modifiers on BD in Jinan.

Methods: Daily data of BD cases and meteorological factors from 2005 to 2013 were collected. A generalized additive model (GAM) was conducted to explore the relationship between meteorological factors and BD. Then a distributed lag non-linear model (DLNM) was developed to assess the lag and cumulative effect. Finally, the modified effect between temperature and other meteorological factors on BD was explored by the GAM and a weather-stratified model.

Results: A total of 11,738 cases of BD were notified over the study period. The exposure-response relationship between temperature and BD was liner with a single threshold value of 0 °C. Results of DLNM showed that after temperature exceeds the threshold, each 5 °C rise in temperature caused a 19% (RR = 1.19, 95% CI: 1.14-1.24) increase in the number of cases of BD at lag 0. The analysis of cumulative effects showed that each 5 °C rise in temperature can increase the number of cases by 61% (RR = 1.61, 95% CI: 1.58-1.63) at lag 0-lag 7 days. The effect modification of the association between temperature and BD by humidity was observed in our study, while the modification by precipitation and wind speed were not statistically significant. The risk of BD was highest when temperature and humidity were both high.

Conclusions: Our study indicates that temperature is significantly associated with the risk of BD in the study area, and the effect can be modified by humidity. Public health professionals and medical service providers should pay more attention BD prevention and control when the weather condition of both high temperature and high humidity would occur.