Weather impacts COVID-19 transmission primarily via mechanisms other than changes to human mobility

What is it about?

Four years after the beginning of the COVID-19 pandemic, a growing body of evidence suggests that SARS-CoV-2 is impacted by weather, though it remains unclear what drives these relationships. Generally, we see more COVID-19 in the cooler winter months, similar to seasonal respiratory infections like influenza, and RSV. One prevailing hypothesis is that people spend more time indoors in cooler weather, and the time spent indoors in poorly ventilated spaces and in close contact with others causes increased spread of COVID-19. However, the findings of this analysis do not support this hypothesis. Rather, in this study, we found that weather appears to have impacted COVID-19 transmission primarily via mechanisms other than via weather-associated changes in human movement patterns.

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Photo by Austin Scherbarth on Unsplash

Photo by Austin Scherbarth on Unsplash

Why is it important?

Our results suggest that weather may impact SARS-CoV-2 by directly altering the probability that the virus is successful in spreading from person to person. In other words, at certain temperatures or humidity levels, the virus may survive longer and, therefore, the probability of transmission is higher. Our results also suggest that, at least in the first year of the COVID-19 pandemic that we examined, weather probably wasn’t causing people to spend more time indoors in ways that lead to increased spread of infection. Notably, this was a time when stay at home orders, work from home and remote school policies were occurring. Overall, the results of this study suggest that measures that specifically aim to reduce the probability of transmission, such as vaccination or improved ventilation, may be needed to reduce weather-driven changes in the spread of COVID-19.

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