“Here comes the sun. Here comes the sun. And I say it’s all right.” -The Beatles
The novel coronavirus is bringing nations to their knees. More than a million people around the world are known to be infected with COVID-19, the disease that’s on track to kill as many as a quarter of a million Americans in the next few months, even with mitigating measures in place.
But is the virus any match for the desert sun?
“Looks like by April, you know, in theory, when it gets a little warmer, it miraculously goes away,” President Donald Trump opined in February, prompting ridicule and lampooning.
Many experts say there is scientific reason to believe the ultraviolet rays of the sun will thwart the spread of the virus. Others have their doubts.
“Although it has been discussed as a possibility, this is another one of those unknowns,” says Dr. Brian Labus, a UNLV epidemiologist and a member of Gov. Steve Sisolak’s medical advisory team on COVID-19. “I don’t think we can say what will happen when summer arrives.”
“Temperature, UV light, and humidity all play a role in environmental survivability of the virus, so a change in the weather could change the course of the outbreak,” says Labus.
But there’s a downside, he says, to our dry heat.
“Drier air can also dry out the nasal passages and make it easier for the virus to gain entry to the body.”
“It is not yet known whether weather and temperature impact the spread of COVID-19,” says the Centers for Disease Control website. “Generally coronaviruses survive for shorter periods of time at higher temperatures and higher humidity than in cooler or dryer (sic) environments. However, we don’t have direct data for this virus, nor do we have direct data for a temperature-based cutoff for inactivation at this point.”
The CDC goes on to say the temperature necessary to kill the virus would also depend on factors such as surface and environment.
A study published in February by researchers at Harvard University compared the spread of the disease in China, Thailand, Singapore, Japan, South Korea and Taiwan and found “changes in weather alone (i.e., increase of temperature and humidity as spring and summer months arrive in the North Hemisphere) will not necessarily lead to declines in COVID-19 case counts without the implementation of extensive public health interventions.”
Another study examined cases of COVID-19 in China between January 2 and February 29. It found 10 degrees Celsius (50 degrees Fahrenheit) to be the optimal temperature for spread and decreased transmission at higher and lower temperatures.
“COVID-19 incidence changed with temperature as daily incidence decreased when the temperature rose,” the researchers wrote.
Researchers for yet another study, this one from Beihang University in China, found an increase of just one degree Celsius can reduce the virus’ basic reproductive number (RO) by .0383, while a one-degree increase in relative humidity lowers the virus’ RO by .0224.
“This result is consistent with the fact that the high temperature and high humidity significantly reduce the transmission of influenza,” the researchers wrote. “It indicates that the arrival of summer and rainy season in the northern hemisphere can effectively reduce the transmission of the COVID-19.”
Rumors about the ability of heat to kill the virus are rampant, mostly on social media. Unsubstantiated suggestions for killing the virus range from increasing body temperature by soaking in a steaming hot bath to sweating it out in a sauna.
The World Health Organization’s “myth buster” page debunks some of the misinformation.
“Exposing yourself to the sun or to temperatures higher than 25c degrees DOES NOT prevent the coronavirus disease (COVID-19),” says the WHO website. “You can catch COVID-19, no matter how sunny or hot the weather is. Countries with hot weather have reported cases of COVID-19.”
Evidence of this and other coronaviruses surviving the heat is indeed ample.
In 2015, the MERS coronavirus spread in Saudi Arabia in August, when average temperatures range from a low of 85 degrees to a high of 110.
Australia, where summer has given way to autumn, has 5,108 confirmed cases and 24 deaths as of April 2 and is only now getting a grip on COVID-19’s spread through increasingly severe distancing and other mitigating measures.
Spring breakers flocked last month to balmy Florida to frolic in the sun. The state is now emerging as a COVID-19 hot spot.
While previously identified coronaviruses generally spread less in summer, it may have more to do with human behavior than the virility of the viruses, experts say.
Viruses thrive in cold, dry climates. People spend more time inside in close quarters in winter. They’re also exposed to less ultraviolet light.
“Normally, when the weather warms up, we spend more time outside and we open our windows and increase ventilation in our homes,” says Labus. “This decreases our contact with others and can decrease the risk of spreading diseases. However, with schools and businesses closed, we have already created an unprecedented shift in our patterns of behavior and interaction.”
Vaccinations for COVID-19, which are undergoing trials, would put all nations on equal footing in preventing the spread, regardless of climate.
Currently, even if warmer temperatures reduce transmission of the novel coronavirus in the Northern Hemisphere, without a vaccine, the virus is likely to spread as colder climates descend on the Southern Hemisphere, setting up an alternating pattern of recovery and infection every six months.
That could be an especially troublesome prospect for tourist destinations such as Las Vegas.