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| Coronavirus cases are on the rise in many areas of the country, and so are summer's temperatures. But a new understanding of how the virus may be spreading is leaving many to wonder whether it's safe to blast the air conditioning during the height (and heat) of the pandemic.
The answer? It's not entirely clear yet — especially when it comes to crowded indoor spaces. But there are some things you can do to lower your risk for a coronavirus infection while still staying cool this summer.
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New evidence emerges about airborne transmission
Public health experts for months have warned about the possibility of airborne transmission — or the spread of the virus through tiny exhaled particles (aerosols) that can linger in indoor air and travel farther than 6 feet. (Large respiratory droplets produced when someone coughs or sneezes, on the other hand, are quicker to fall to the floor or a nearby surface.) And in early July, 239 scientists in 32 countries published a letter calling on the World Health Organization (WHO) to acknowledge the role of airborne transmission in the spread of the coronavirus.
"All of the data we are seeing from bars and from indoor locations, a choir practice that led to 60 people getting infected, I think there's plenty of evidence that aerosols are really a major source of spread,” Ashish Jha, M.D., director of Harvard's Global Health Institute, explained to a group of reporters on a recent media call.
About one week after the scientists made their case, the WHO modified its stance on aerosol transmission and recognized these tiny droplets may be a bigger issue than previously thought.
"It's nothing to be feared,” Joseph Allen, assistant professor of exposure assessment science at the Harvard T.H. Chan School of Public Health, says about the latest understandings of aerosol transmission. “It just means that we have to recognize it's happening so we can apply the appropriate control strategies” — including how we circulate air in buildings.
Different air conditioning systems distribute air in different ways — from single window units that cool smaller spaces to complex HVAC systems that regulate temperatures in large buildings. One thing they have in common, however, is that “a lot of the air is recirculated,” albeit at varying percentages, explains Linsey Marr, the Charles P. Lunsford professor of civil and environmental engineering at Virginia Tech and an expert in aerosol science. “And when you recirculate that air, that means that the virus is still sticking around in that building, rather than being replaced by more outdoor air, which presumably is virus-free.”