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This Is How Coronavirus Will Most Likely Enter Your Body Indoors

Where you are standing in a room can make you more likely to spread or become infected with COVID-19
Two young female friends chatting over coffee in cafe.

"Outdoors is better than indoors," Dr. Anthony Fauci, the nation's leading coronavirus expert has repeated several times throughout the pandemic. In case you are curious why, exactly, this is the case, a new study courtesy of University of Minnesota scientists hopes to explain it to you. 

The not-yet peer-reviewed report, published online July 28 on the website arXiv, explains how the virus travels via respiratory droplets released when an individual coughs, sneezes, talks, sings, or yells, and makes its way around the room. Researchers hope their information will prove beneficial in the reopening of businesses—such as movie theaters and concert venues—as well as schools. 

The Virus 'Hitches a Ride'

Mechanical engineering associate professor Jiarong Hong and assistant professor Suo Yang modeled the airborne virus transmission through aerosols, released from our mouths when we exhale or speak. They found that when an infected person releases the tiny infected droplets, the SARS CoV-2 virus "hitches a ride" on the aerosols, which then land on nearby surfaces or are inhaled by other people. 

"In general, this is the first quantitative risk assessment of the spatial variation of risks in indoor environments," Hong said in a press release. "You see a lot of people talking about what the risks are of staying in confined spaces, but nobody gives a quantitative number. I think the major contribution we've made is combining very accurate measurements and computational fluid dynamics simulation to provide a very quantitative estimate of the risks."

Hong and Yang used precise experimental measurements of aerosols that were released by eight asymptomatic individuals with COVID-19. They then numerically modeled the external flow of the virus through the air in three different interior spaces: an elevator, a classroom, and a supermarket. 

They also compared how the virus was impacted by varying levels of ventilation and also spacing amongst room occupants. In the indoor spaces, they found that good ventilation filters some of the virus out of the air, but may leave more viral particles on surfaces. For example, in the classroom setting, which involved an asymptomatic teacher consistently talking for 50-minutes, only 10 percent of the aerosols were filtered out with the majority of particles being deposited on the walls. 

Vortexes Form

"Because this is very strong ventilation, we thought it would ventilate out a lot of aerosols. But, 10 percent is really a small number," Yang explained. "The ventilation forms several circulation zones called vortexes, and the aerosols keep rotating in this vortex. When they collide with the wall, they attach to the wall. But, because they are basically trapped in this vortex, and it's very hard for them to reach the vent and actually go out."

In each scenario, the researchers also mapped the air flow in order to identify "hot" spot locations of the virus. They noted that if a room was well-ventilated with individuals effectively organized, disease spread could be mitigated. For example, in a setting such as a classroom, if the teacher was placed directly under an air vent, virus aerosols spread significantly less throughout the room. 

"After our work goes out, I think more people will ask for help because I think many businesses reopening will have this need — movie theaters, drama theaters, any place with large gatherings," Yang said. "If you do a good job, if you have good ventilation at the right location, and if you scatter the seating of the audience properly, it could be much safer."

As for yourself: Wear your face mask, get tested if you think you have coronavirus, avoid crowds (and bars, and house parties), practice social distancing, only run essential errands, wash your hands regularly, disinfect frequently touched surfaces, and to get through this pandemic at your healthiest, don't miss these 37 Places You're Most Likely to Catch Coronavirus.

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