Objective  To investigate the association of daily mean temperature and daily mean relative humidity with the incidence of other infectious diarrhea and their lag effects in Suzhou , Anhui province, identify the populations at high-risk, and provide evidence for the development of precise prevention and control strategies.

Methods  The daily incidence data of other infectious diarrhea and concurrent meteorological data in Suzhou from 2020 to 2024 were collected. Spearman rank correlation analysis was used to select appropriate meteorological factors. Distributed lag nonlinear model (DLNM) was used to quantify the association of daily mean temperature and daily mean relative humidity with the incidence of other infectious diarrhea.

Results A total of 38 473 cases of other infectious diarrhea were reported in Suzhou from 2020 to 2024, the male to female ratio of the cases was 1.05∶1. The highest proportion of the cases (50.67%) was observed in people aged 14−60 years. DLNM results showed that, using the median daily mean temperature of 16.90°C as reference, temperature ranges of −8.00°C to 2.00°C and 22.00°C to 32.00°C were associated with the increased risk. The cumulative risk was highest at −8.00°C (RR=2.71, 95%CI: 1.47−4.98). Low temperature posed the highest cumulative risk for the population under 14 years old (RR=1.97, 95%CI: 1.07−3.63). High temperature had an immediate effect on the risk for people aged 14−60 years, and the cumulative risk over a 21-day lag was also highest in this age group (RR=1.96, 95%CI: 1.47−2.61). Using the median daily mean relative humidity of 70.93% as reference, a relative humidity range of 39.00%−70.00% was a risk factor for other infectious diarrhea over a 21-day cumulative lag, with the highest risk at 51.00% (RR=1.34, 95%CI: 1.20−1.51). A range of 72.00%–84.00% showed a protective effect, with the best protective effect at 81.00% (RR=0.88, 95%CI: 0.82−0.95). Low humidity posed the highest cumulative risk for the population under 14 years old (RR=1.50, 95%CI: 1.15−1.96). The effect of high humidity on the incidence of other infectious diarrhea in the whole population was not significant.

Conclusions Daily mean temperature and daily mean relative humidity have significant lagged effects on the risk for other infectious diarrhea in Suzhou. Low temperature, high temperature, and low humidity increase the morbidity risk in specific populations. It is suggested to develop differentiated prevention and control strategies for other infectious diarrhea for different temperature and humidity ranges to reduce the risk of disease.