Shortly after the coronavirus emerged, scientists quickly discovered the pathogen’s structure, its entire genetic sequence and most of the ways it spreads, but one concept remains a mystery: weather’s role in its transmission.
Researchers have developed models to simulate how temperature, rain, humidity and pressure can influence how the coronavirus spreads, but real life is more complicated than what a computer can predict.
Some studies have shown that high temperatures can prove hostile for a virus’s survival, but this doesn’t mean it still cannot be passed from one person to another.
For now, scientists must use their understanding of how other diseases spread to predict the best- and worst-case scenarios for this one.
“One should not assume that we are going to be rescued by a change in the weather,” Dr. Anthony Fauci, the nation’s leading epidemiologist and member of the White House coronavirus task force, told ABC’s Good Morning America.
“You must assume that the virus will continue to do its thing,” he added.
It’s known that respiratory infections such as the flu and common cold are seasonal, meaning they tend to resurface during the winter when conditions are cold and dry.
Cold air irritates nasal passages and airways, “which makes us more susceptible to viral infection,” Simon Clarke, a cellular microbiology expert at the University of Reading in England, told Reuters.
The mucus in your nose usually traps and blocks viruses and bacteria from entering your body, but wintry conditions can make “normally gooey mucus drier and less efficient” at doing its job, National Geographic reported.
Virus particles hiding in respiratory droplets from coughs and sneezes bode well in dry conditions, too, because they can float in the air for longer, giving them more time and room to latch onto more people, according to experts.
People also spend more time indoors, which makes it easier for viruses to hop from one person to the next.
HOW COULD SUMMER CHANGE VIRUS TRANSMISSION?
In the summer, more people are out and about and the humid conditions allow viral droplets to gather more moisture than usual, eventually becoming too heavy and dropping to the ground.
Sunlight and its accompanying ultraviolet radiation can also kill viruses that land on surfaces, according to Ian Lipkin, director of Columbia University’s Center for Infection and Immunity.
“[UV light] almost sterilizes surfaces. If you’re outside, it’s generally cleaner than inside simply because of that UV light,” which is used in hospitals to disinfect medical equipment, Lipkin told Nat Geo.
One study showed that after 30 minutes under 133 degrees Fahrenheit, coronavirus particles were no longer viable, according to a paper published in April in the journal The Lancet Microbe.
But these extremely high temperatures don’t exist where people live, making it hard to understand if an 80-degree summer will have the same effect.
Current transmission rates in countries with hot and humid weather tell a different story.
As of May 26, Brazil became the country with the second most confirmed coronavirus cases in the world with more than 374,000 cases, after the U.S., according to Johns Hopkins University.
Harvard University recently compiled COVID-19 infection and weather data from 3,739 locations between Dec. 12 and April 22 to understand how weather and air pollutants affect coronavirus transmission.
“Our projections suggest warmer temperature and moderate outdoor ultraviolet exposure may offer a modest reduction in transmission,” the researchers said in their working paper.
Their findings match those of similar studies on the topic, which can help “with efforts to contain the pandemic and build response capacity,” but other factors such as “population density, cultural practices and individual and policy responses” also play major roles in viral spread.
The researchers concluded that “upcoming changes in weather alone will not be enough to fully contain the transmission of COVID-19.”
But weather could make a second coronavirus wave likely, and worse than the first, Centers for Disease Control and Prevention Director Robert Redfield told The Washington Post.
If seasonal, COVID-19 can combine with the regular winter flu, doubling the burden on hospital resources and staff, Redfield said.
Experts agree that because the coronavirus is making its first rounds in humans, the majority of the world remains highly susceptible to infection, meaning vulnerability is likely to overwhelm any effect temperature and weather have on virus transmission.
“Summer is not going to make this go away,” Dionne Gesink, an epidemiologist at the Dalla Lana School of Public Health in Canada, told Science Alert. “It’s important people know that.
“On the other hand … public health interventions are really important because they’re the only thing working right now to slow the epidemic,” she added.
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