Study: Data Show Lower Daily Temperatures Lead to Higher Transmission of COVID-19

Understanding the impact of seasonal temperature changes on transmission of COVID-19 is an important factor in reducing the spread of the virus in the future, according to a study conducted by researchers at the University of Louisville.

SARS-CoV-2 belongs to a family of human coronaviruses, most of which are characterized by increased transmission in cooler, less humid months and decreased transmission in warmer, more humid months.

The researchers theorized that atmospheric temperature would affect transmission of SARS-CoV-2 by comparing daily low temperature data and logged cases of COVID-19 in 50 countries in the Northern Hemisphere between January 22 and April 6, 2020.

The findings showed that as temperatures rose, the rate of new cases of COVID-19 decreased. Further, the analysis showed that between 30 and 100 degrees Fahrenheit, a 1-degree Fahrenheit increase in daily low temperature was associated with a 1% decrease in the rate of increase in COVID-19 cases. A 1-degree decrease in temperature was associated with an increase in that rate by 3.7%. The results were able to be obtained by lockdowns, masking, or other social efforts to contain the virus, according to the study authors.

"Although COVID-19 is an infectious disease that will have non-temperature dependent transmission, our research indicates that it also may have a seasonal component," said study author Aruni Bhatnagar, PhD, director of the Brown Envirome Institute, in a press release. "Of course, the effect of temperature on the rate of transmission is altered by social interventions like distancing, as well as time spent indoors and other factors. A combination of these factors ultimately determines the spread of COVID-19."

The research team concluded that summer months are associated with slowed transmission of COVID-19, as in other seasonal respiratory viruses. This seasonal effect could be useful in local planning for social interventions and timing of resurgence of the virus, according to the study authors.

The data indicate that the correlation between temperature and transmission was much greater than the association between temperature and recovery or death from COVID-19.

"This understanding of the SARS-CoV-2 temperature sensitivity has important implications for anticipating the course of the pandemic," said study author Adam Kaplin, MD, PhD, of Johns Hopkins, in a press release. "We do not know how long the currently available vaccines will sustain their benefits, nor what the risks are of new variants developing over time if the Northern and Southern Hemispheres continue to exchange COVID-19, back and forth across the equator, due to their opposing seasons. But it is reasonable to conclude that this research suggests that, like other seasonal viruses, SARS-CoV-2 could prove to be extremely difficult to contain over time unless there is a concerted and collaborative global effort to work to end this pandemic."

REFERENCE

Data show lower daily temperatures lead to higher transmission of COVID-19. EurekAlert! https://www.eurekalert.org/pub_releases/2021-02/uol-dsl021921.php. Published February 19, 2021. Accessed February 23, 2021.