If you’ve been hoping warmer summer weather might kill off coronavirus, you’re out of luck, according to researchers.
A University of Toronto study of 144 areas around the world with over 375,000 COVID-19 cases by March 27 found no evidence that hot weather can help in the fight against the pandemic.
The study, which was published in the Canadian Medical Association Journal on May 8, is the first peer-reviewed global study outside of China to show that climate is unlikely to factor in the transmission of the virus.
The researchers found countries with warm climates had no advantage over colder climates when it came to virus spread. Singapore, Ecuador and Louisiana saw cases of COVID-19 rise as temperatures climbed over 30 degrees Celsius.
Many people held out hope that warm weather would precipitate a decline in cases because the high heat and humidity of summer reduces the spread of colds and flu. But that’s also because many people are at least partially immune to the flu, and that immunity builds over time as people are vaccinated. People have no immunity to coronavirus, the researchers said, so any weather could be considered favourable for it to thrive.
However, the U of T study had encouraging findings: countries that enacted significant public health interventions, including restrictions on mass gatherings and school closures, have been effective at curbing spread.
“Summer is not going to make this go away,” said epidemiologist, professor and study author Dionne Gesink in a statement. “On the other hand, the more public health interventions an area had in place, the bigger the impact on slowing the epidemic growth. These public health interventions are really important because they’re the only thing working right now to slow the epidemic.”
The report includes a comparison between Greece, which shut its schools down 14 days after its first positive test and banned public gatherings, and Singapore, which had its first case in January, but didn’t shut schools down until April 8 and allowed public gatherings.
“At the height of each country’s outbreak, Singapore suffered roughly 10 times as many cases as Greece,” the report states.
Researchers also found that high humidity might help fight the virus, though to a minimal degree, “possibly because aerosol droplets fall to the ground more quickly or virus particles become unstable in wet, heavy air.” Knowing that the virus cannot spread as easily in open-air areas, this suggests outdoor activities might just be a little bit safer in the summer weather, as long as we keep up with social distancing.
Still, the bottom line remains that even if humidity has a slight impact, weather changes will not make anywhere near a significant change to virus transmission, and it certainly won’t spell an end to social distancing any time soon.
