In a new study, researchers found that while the rate of COVID-19 incidence does decrease with warmer temperatures up until 52 degrees F, further warmer temperatures do not decrease disease transmission strongly.
They found a higher UV index also assists in slowing the growth rate of new cases, but the overall impact remains modest.
The research was conducted by a team at Mount Auburn Hospital.
It is well known that rates of transmission of some respiratory viruses, including influenza, tend to fall during the summer months.
As COVID-19 has spread across the globe, questions have been raised about whether warming temperatures, humidity, and UV index might slow, or even halt, the spread of SARS-CoV-2, the virus that causes COVID-19.
These effects on virus transmission will be important to understand as warmer months ease in and states across the country consider and implement reopening plans.
To answer these questions, the team looked at the impact of temperature, precipitation, and UV index on COVID-19 case rates in the United States during the spring months of 2020.
The team analyzed daily reported cases of SARS-CoV-2 infection across the United States from January 22, 2020, through April 3, 2020, and estimated associations between temperature, precipitation, UV Index, as tracked from the National Centers for Environmental Information, and rate of case increase.
The team found that while the rate of virus transmission may slow down as the maximum daily temperature rises to around 50 degrees, the effects of temperature rise beyond that don’t seem to be significant.
Based on the analysis, the modest association suggests that it is unlikely that disease transmission will slow dramatically in the summer months from the increase in temperature alone.
In addition to examining how temperature changes between January and April of 2020 impacted the spread of SARS-CoV-2, the team modeled what the impact would be if a state remained within a maximum temperature range, demonstrating five different scenarios: less than 30 degrees F (-1 C), between 30-40 degrees F (-1 C – 4 C), between 40-50 degrees F (4 C – 10 C), between 50-60 degrees F (10 C – 16 C), and over 60 degrees F (16 C).
The lowest rate of new cases was observed on days where the temperature was above 50 degrees F five days earlier.
The highest increase in infection rates was detected on days when the maximum temperature was below 30 degrees F.
The Centers for Disease Control and Prevention has stated that the COVID-19 pandemic may worsen in the fall and winter as temperatures drop.
The researchers also caution that the disease may get worse in the fall and winter months.
The lead author of the study is Shiv T. Sehra, MD, Director of the Internal Medicine Residency Program at Mount Auburn Hospital.
The study is published in Clinical Infectious Diseases.
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