Q: Does warmer weather keep COVID-19 from spreading?
A: Warmer weather is not expected to make a difference in transmission rates this summer. The virus already spread rapidly in countries with summer climates, including Iran and Australia, suggesting warmer temperatures in the United States won’t change the rate of transmission. Previous coronaviruses, including those that caused severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), did not spread at different rates during different seasons.
Dr. Francis Collins, director of the National Institutes of Health, writes that COVID-19 is unlikely to show seasonal patterns of transmission until herd immunity develops. The spread of the virus depends primarily on the proportion of the population that is immune to it. As long as relatively few people are immune, the virus is likely to continue spreading rapidly.
Researchers who have used mathematical models to predict the future spread of the virus believe warm temperatures may help slow transmission in combination with safe treatments and vaccines once they are developed. For now, Dr. Collins writes, “physical distancing will remain our best weapon into the summer to slow or prevent the spread of COVID-19.”