As the United States heads deeper into spring, it has been suggested that warmer temperatures will halt the spread of the new coronavirus and the COVID-19 disease it causes. Several small, preliminary studies indicate the virus could follow a pattern similar to flu and cold viruses, which significantly wane as the weather warms up.
The reality is, although the nation and the rest of the Northern Hemisphere will likely see a tapering off of cases, “we should expect infections to drag on, regardless of warming weather,” said University of Washington epidemiologist and infectious disease specialist Gerard Cangelosi, who’s involved in COVID-19 studies.
“The dam just broke and the valley is filling with water. It will continue to fill regardless of the weather,” he said. “Most likely, seasonality will slow down expansion of the disease, but it won’t reverse it.”
It is well established that most respiratory diseases, ranging from the flu and common cold to tuberculosis, spread more readily in the cold, dry air of winter, while losing their punch in the warm, moist air of summer. This is partly to do with how long the germs can linger in the air or adhere to surfaces while remaining contagious to humans.
However, it’s too soon to know if the coronavirus, or SARS-CoV-2, will follow a similar pattern, Cangelosi said.
“A year ago, we hadn’t even heard of it. We simply don’t know how COVID-19 cases will change with the seasons,” he said. To complicate matters, with no natural immunity in the population, the virus has more opportunities for transmission “no matter what time of year,” he said.
Harvard epidemiologist Marc Lipsitch agrees that warm weather alone won’t put a big dent in the spread of coronavirus.
“Based on the analogy of pandemic flu, we expect that SARS-CoV-2, as a virus new to humans, will face less immunity and thus transmit more readily even outside of the winter season,” he wrote in a widely cited article posted on Harvard’s School of Public Health website. “Changing seasons and school vacation may help, but are unlikely to stop transmission.”
Weather conditions such as cold temperatures, heavy rains, flooding and heatwaves have well-documented effects on the spread of infectious diseases, but it’s too soon to know what role weather will play with COVID-19, said meteorologist Nic Loyd of Yakima.
“Certain weather conditions can boost transmission of pathogens, but too little is known about this new virus to say how it will be impacted. We just don’t have solid data yet,” he said.
One possibility is that ultraviolet light from the summer sun could neutralize coronaviruses by modifying their RNA, said UW’s Cangelosi.
“The UV radiation wouldn’t destroy the virus completely, but it might reduce its numbers somewhat,” he said, adding that outside surfaces such as picnic tables, door handles and playground equipment might have fewer viable viruses adhering to them.
But the most immediate positive impact of warm weather will probably have more to do with how humans react than how the virus reacts, Cangelosi said.
When the weather is cold, people spend more time indoors and have closer contact with people who might be infected. Now that temperatures are warming up, people will be drawn outdoors.
“As long as we continue to practice social distancing, infections could slow down a bit,” he explained.
Ironically, the silver lining of coronavirus is the time of year it was unleashed, he said.
“Had the dam broke in November, we’d be faced with a much bigger problem. With summer coming, I see some hope.”
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