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Disclosures: The authors report no relevant financial disclosures.
May 08, 2020
2 min read

Seasonality will likely only have ‘minor' impact on COVID-19 epidemiology

Disclosures: The authors report no relevant financial disclosures.
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Seasonality will likely have only a minor role in the epidemiology of COVID-19 compared with public health interventions such as school closures and social distancing, which have been shown to have a major impact, according to a prospective cohort study in the Canadian Medical Association Journal.

“It is unclear whether seasonal changes, school closures or other public health interventions will result in a slowdown of the current COVID-19 pandemic,” Peter Jüni, MD, FESC, director of the Applied Health Research Centre at the Li Ka Shing Knowledge Institute of St. Michael’s Hospital and professor in the department of medicine and the Institute of Health Policy, Management and Evaluation at the University of Toronto, and colleagues wrote. “We aimed to determine whether epidemic growth is globally associated with climate or public health interventions intended to reduce transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).”

Jüni and colleagues performed a prospective cohort study of all 144 geopolitical areas throughout the world with at least 10 cases and local transmission as of March 20, 2020, excluding China, South Korea, Iran and Italy. According to the study, researchers used weighted random-effects regression to examine the relationship between epidemic growth and latitude, temperature, humidity, school closures, limits on mass gatherings and the implementation of social distancing during an exposure period lasting from March 7 through March 13.

In total, the study included 375,609 cases. There were few or no correlations between epidemic growth of COVID-19 and geographic latitude or temperature during the exposure period. Weak negative associations with relative humidity (ratios of rate ratios [RRR] per 10%, 0.91; 95% CI, 0.85-0.96) and absolute humidity (RRR per 5 g/m3, 0.92; 95% CI, 0.85-0.99) were noted. Strong associations was observed for restrictions of mass gatherings (RRR, 0.65; 95% CI, 0.53-0.79), school closures (RRR, 0.63; 95% CI, 0.52-0.78) and social distancing (RRR, 0.62; 95% CI, 0.45-0.85). In a multivariable model, the researchers observed a strong association with the number of implemented public health interventions (P for trend = .001), whereas the correlation with absolute humidity was no longer significant.

“Taken together, these findings suggest that seasonality is likely to play only a minor role in the epidemiology of COVID-19, while public health interventions (school closures, restricting mass gatherings, social distancing) appear to have a major impact,” the authors concluded. “The important effect of public health interventions needs to be weighed carefully against potential economic and psychosocial harms when deciding when and how to lift restrictions.” – by Caitlyn Stulpin

Disclosures: The authors report no relevant financial disclosures.