Keeping up with coronavirus is the world's least favorite reality show. If your state is gradually lifting its lockdown, it's important to know how coronavirus might spread in your local enclosed café, as opposed to out at the park. Science says we're more exposed to coronavirus in indoor spaces than we are outdoors.
"Coronavirus often spreads more easily indoors compared to outdoors," Ravina Kullar, Pharm.D., an epidemiologist who specializes in protecting vulnerable people in care homes from infectious diseases, tells Bustle. "The virus is more easily transmitted when you are in closed areas, with less ventilation or room for airflow, and also for an extended period of time."
You can catch coronavirus in the same way regardless of where you are: through inhaling or being exposed to viral droplets that then infect your body. But other factors, like lack of air movement and close proximity to other people, mean indoor spaces put you at a higher risk.
Here's why you should always try to meet up with others outdoors, or at least in a place with open doors and windows.
How Coronavirus Spreads Indoors
Research has shown that coronavirus largely spreads through droplets in peoples' coughs and sneezes, which then fall on surfaces and can be transferred to others. It's like a horrible, sticky, invisible rain, and a lack of air circulation means it falls close by or can be breathed in. "If restaurants close windows, people end up breathing in a lot more air that has been exhaled by others, which is a breeding ground for transmission," Kullar says.
Air conditioning also won't help. "Air conditioners typically recirculate indoor air to reduce energy use," Kullar says. "Most air-conditioning units do not provide enough fresh air given the risk of COVID-19 in more densely-populated indoor spaces such as bars and restaurants." Right now, she says, many buildings need to upgrade their air-conditioning systems to take in more fresh air from the outside world.
And the longer you spend in an indoor space with an infected person, the higher your risk is of catching the coronavirus. "Several case studies of COVID-19 outbreaks have shown the dangers of spending a long time in an enclosed indoor space with an infected person, including at a choir practice in Washington state, a restaurant in China and a fitness studio in South Korea," Kullar says. Given that a new survey by the Office of National Statistics in the U.K. has found up to 78% of people who test positive for coronavirus have no symptoms whatsoever, chances are that one of the people in a crowded restaurant with you has it.
"Outdoors, the presumption is that the remarkably larger volume of air and the usual movement of that air with wind or breezes would dilute the number of particles, and disperse them more widely," Dr. John A. Sellick D.O., professor of medicine in the division of infectious diseases at the University at Buffalo/SUNY, tells Bustle. This makes contracting coronavirus less likely, he says — as long as you're not standing too close to other people.
Airborne Transmission May Mean Indoor Spaces Are Less Safe
We're all using precautions like masks and hand-washing because COVID-19 appears to spread through droplets in other peoples' coughs. But something else might be happening, too. The World Health Organization (WHO) has now said "evidence is emerging" that coronavirus might also spread through airborne transmission. Illnesses that use airborne transmission linger in the air and can be blown around because their particles are so small — less than 5 micrometers in diameter, according to WHO's definition.
"Larger droplets, the ones that can be felt when coughing or sneezing, mostly fall to the ground a very short distance from the patient," Dr. Sellick says. "Smaller droplets, commonly referred to as aerosols or droplet nuclei, can remain suspended in the air and travel longer distances." He says it still seems as if larger droplets play the dominant role in coronavirus, but it's not clear if smaller ones are involved too. A study published in Current Medicine Research & Practice on the aerosol spread of coronavirus found that if the particles can indeed be that small, laughing and talking may also spread coronavirus.
If the coronavirus is also airborne, it may mean that enclosed places are even less safe. To prevent infection, indoor spaces would need to use a lot more fresh air, or install some kind of filtration system on their air conditioning.
How To Protect Yourself Indoors & Outdoors
If you're outside, you still need to maintain social distance. Dr. Sellick points out that you can't rely on wind to blow all coronavirus away. "If you are very close to other people, at parties and on beaches, then the risk of infection would not be completely mitigated just because you're outdoors," he says. Wear masks if you're likely to encounter a lot of people on your beach trip, and avoid crowds if you can.
Meeting others inside? Kullar says you should always wear a mask or face shield, maintain a six-foot distance from others, and wipe down all frequently touched surfaces. "Your risk of getting COVID-19 ― whether you’re inside or outside ― is lower overall if you take these steps," she says. Especially if you live with someone who's vulnerable to severe illness, reconsider going to that patio-less restaurant — even if it's reopening.
Ravina Kullar Pharma.D. MPH
John A. Sellick DO MS
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