Impact of climate and public health interventions on the COVID-19 pandemic

Bottom Line:

Epidemic growth is associated with humidity and the degree of public health measures including social distancing, school closures, and restrictions on mass gatherings.


Jüni, P. et al. Impact of climate and public health interventions on the COVID-19 pandemic: A prospective cohort study. CMAJ (2020).

Date Published:

25 May 2020


The decline of influenza epidemics during summers has been attributed to higher temperature, humidity, solar radiation, and temporary school closures for summer breaks. Responses to the COVID-19 pandemic have involved implementing social distancing measures, school closures, and policing mass gatherings. A prospective cohort study was performed with 144 geopolitical areas to determine the impact of these interventions and climate on the COVID-19 epidemic growth. The primary exposure, geographic latitude, and secondary exposure variables (mean temperature, humidity, school closures, restrictions on mass gatherings, and social distancing measures) were collected during the exposure period, March 7th to 13th, 2020. A one-week follow-up period was set to 14 days following the start of the exposure period to determine a rate ratio between current cumulative case count and cumulative case count one week earlier. This cumulative frequency assessed for epidemic growth while accounting for reporting and detection differences across various geopolitical areas. Weighted random-effects regression analyses revealed a weak association of relative and absolute humidity to epidemic growth and no association with geographic latitude nor temperature during the exposure period. Conversely, public health interventions, specifically restrictions of mass gatherings, school closures, and social distancing measures, were associated with decreased epidemic growth with co-intervention of 2-3 measures having the greatest impact. Although the individual impact of each intervention on attenuating epidemic growth could not quantified, these findings illustrate the significant effectiveness of public health measures and will shape future approaches to lifting restrictions.

Summary by Julia Kim