During summer the transmission rates of most respiratory viral infections such as influenza will drop.
Several studies on SARS-CoV-2 have shown that its survival rate is shorter in higher temperatures and UV light inactivates the virus.
However, until now the effects of temperature, UV light, and precipitation on how quickly the virus is transmitted between people has not been investigated.
The question is whether warmer temperature, UV light, and humidity can lower or even curb the rapid spread of SARS-CoV-2.
A research team assessed the link between weather conditions including precipitation, UV index, and temperature and the number of coronavirus cases during spring 2020 in the U.S.A..
They found that higher temperature up to 52 degrees Fahrenheit (11 degrees Celsius) reduced the incidence of COVID-19.
However, any higher temperatures didn’t have much impact on reducing disease transmission.
Precipitation patterns didn’t affect the spread rate but a higher UV index was found to lessen the number of new cases.
Dr Shiv T Sehra, the study’s first author, said:
“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 our 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.”
Furthermore, they checked if changes in temperature had any impact on the spread of SARS-CoV-2 between January and April 2020.
They used a model for five different scenarios as follows: above 60 degrees °F (16 °C), between 50-60 degrees °F (10 °C – 16 °C), between 40-50 degrees °F (4 °C – 10 °C), between 30-40 degrees °F (-1 °C – 4 °C), and less than 30 degrees °F (-1 °C).
The days that the temperature was above 50 degrees °F showed the lowest number of new COVID-19 cases.
While the days where the temperature was below 30 degrees °F had the maximum hike in infection rates.
According to The Centers for Disease Control and Prevention, through the fall and winter as temperatures drop the coronavirus pandemic might get worse.
Dr Sehra noted:
“Our results are in line with those predictions.
We also caution that the disease may get worse in the fall and winter months.”
One study limitation is that the collected data reflect spring when the daily maximum temperature was below 70 degrees Fahrenheit (21 degrees Celsius) whereas summer temperatures in most parts of the country will be much higher than that.
Consequently, this study can’t assess the possible effects of temperatures above 70-75 degrees Fahrenheit on COVID-19 virus transmission.
About the author
Mina Dean is a Nutritionist and Food Scientist. She holds a BSc in Human Nutrition and an MSc in Food Science.
The study was published in the journal Clinical Infectious Diseases (Sehra et al., 2020).