Interactive effects of meteorological factors and air pollutants on mumps incidence in Southwest China, 2015–2024

Mumps is a highly infectious respiratory disease; however, the impact of meteorological factors and air pollutants on its prevalence remains unclear. Therefore, this study aims to investigate the independent and interactive effects of these factors on mumps in Chongqing, China, a typical mountainous city with a unique climate and a highly dense population. Data from 23,755 mumps cases reported in the central urban area of Chongqing were selected for analysis during 2015 to 2024. Geodetectors, Distributed Lag Nonlinear Models (DLNM), and bivariate response models were employed to investigate the associations between environmental factors and mumps incidence. Moreover, the interactions between meteorological factors and air pollutants were evaluated by the relative excess risk (RERI). Meteorological factors (temperature, relative humidity) and air pollutants (SO 2 , NO 2 , and CO) were significantly correlated with mumps incidence and showed nonlinear, lagged characteristics. Furthermore, temperature showed an initial increase followed by a decrease in incidence risk, while relative humidity demonstrated an approximate U-shaped relationship. SO 2 , NO 2 , and CO exhibited S-shaped or continuously rising exposure-response curves, respectively. All factors exhibited significant lagged effects within specific lag windows. Mean temperature and CO concentration exhibited a statistically significant synergistic effect on mumps incidence, with RERI and API values of 0.237 (95% CI: 0.032, 0.477) and 0.232 (95% CI: 0.039, 0.39), respectively. The remaining five meteorology–pollutant pairs did not show statistically significant interactions. In summary, temperature, humidity and air pollution showed significant nonlinear, delayed associations on mumps incidence. Additionally, only the temperature and CO interaction showed statistically significant synergy. Not applicable.