Hanging Indoors? Here’s What To Know About Your COVID Risk.

Keeping up with coronavirus is the world's least favorite reality show. Science says we're more exposed to coronavirus in indoor spaces than we are outdoors, so it's important to know how coronavirus might spread at a dinner party, as opposed to out at the park.

"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.

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 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. There's even a website that estimates the COVID risk of small person gatherings in each county in the U.S.

"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 Means 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 it also spreads 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 the World Health Organization (WHO).

"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 smaller particles are also a factor, according to the CDC. A study published in Current Medicine Research & Practice on the aerosol spread of coronavirus found that laughing and talking may also spread coronavirus.

Indoor gatherings have been linked to serious COVID-19 outbreaks. The Washington Post reported in November that spikes in U.S. coronavirus numbers were increasingly caused by "small, private social gatherings" indoors, according to scientists. Superspreader events have taken place inside churches, meatpacking plants, offices, and bars, as well as at private parties and small dinners.

As the coronavirus is airborne, completely enclosed places are unsafe. To prevent infection, indoor spaces 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, maintain a six-foot distance from others, and wipe down all frequently touched surfaces. Minimize the amount of time you spend indoors with others, even when masked; just 15 minutes of close contact with an asymptomatic person can lead to infection, according to the CDC, though ventilation and strict social distancing can provide some protection. Keep windows open and run fans to maximize airflow. "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 anywhere that doesn't have outdoor seating — even if it's really cold outdoors.

Experts:

Ravina Kullar Pharma.D. MPH

John A. Sellick DO MS

Studies cited:

Hamner, L., Dubbel, P., Capron, I., et al. (2020) High SARS-CoV-2 Attack Rate Following Exposure at a Choir Practice — Skagit County, Washington, March 2020. MMWR Morb Mortal Wkly Rep, 69:606–610.

Jang, S., Han, S.H., Rhee, J-Y. (2020) Coronavirus disease cluster associated with fitness dance classes, South Korea. Emerg Infect Dis.

Lu, J., Gu, J., Li, K., Xu, C., Su, W., Lai, Z....Yang, Z. (2020). COVID-19 Outbreak Associated with Air Conditioning in Restaurant, Guangzhou, China, 2020. Emerging Infectious Diseases, 26(7), 1628-1631. https://dx.doi.org/10.3201/eid2607.200764.

Morawska, L., Tang, J. W., Bahnfleth, W., Bluyssen, P. M., Boerstra, A., Buonanno, G., Cao, J., Dancer, S., Floto, A., Franchimon, F., Haworth, C., Hogeling, J., Isaxon, C., Jimenez, J. L., Kurnitski, J., Li, Y., Loomans, M., Marks, G., Marr, L. C., Mazzarella, L., … Yao, M. (2020). How can airborne transmission of COVID-19 indoors be minimised?. Environment international, 142, 105832. https://doi.org/10.1016/j.envint.2020.105832

Ningthoujam R. (2020). COVID 19 can spread through breathing, talking, study estimates. Current medicine research and practice, 10(3), 132–133. Advance online publication. https://doi.org/10.1016/j.cmrp.2020.05.003