The Impact of Cold Ambient Temperature in the Pattern of Influenza Virus Infection

BACKGROUND: Prior literature suggests that cold temperature strongly influences the immune function of animals and human behaviors, which may allow for the transmission of respiratory viral infections. However, information on the impact of cold stimuli, especially the impact of temporal change in the ambient temperature on influenza virus transmission, is limited. METHODS: A susceptible-infected-recovered-susceptible model was applied to evaluate the effect of temperature change on influenza virus transmission. RESULTS: The mean temperature of the prior week was positively associated with the number of newly diagnosed cases (0.107 [95% Bayesian credible interval {BCI}, .106–.109]), whereas the mean difference in the temperature of the prior week was negatively associated (−0.835 [95% BCI, −.840 to −.830]). The product of the mean temperature and mean difference in the temperature of the previous week were also negatively associated with the number of newly diagnosed cases (−0.192 [95% BCI, −.197 to −.187]). CONCLUSIONS: The mean temperature and the mean difference in temperature affected the number of newly diagnosed influenza cases differently. Our data suggest that high ambient temperature and a drop in the temperature and their interaction increase the risk of infection. Therefore, the highest risk of infection is attributable to a steep fall in temperature in a relatively warm environment.