6 key factors to consider when determining your risk of catching the coronavirus in any situation

People wearing protective masks in front of an Apple store in Zurich, Switzerland, on May 13. Arnd Wiegmann/Reuters

Even simple activities like running to the grocery store or hanging out in a park can be mentally taxing these days, since they all require an assessment of our risk of getting the coronavirus. Even as some businesses reopen and states report downward trends in cases, those questions are likely to hover over decisions for years to come.

According to infectious-disease experts, there are several ways to determine how risky an activity or place is. Coronavirus transmission risk is somewhat lower outside than indoors, for example, though the most important factors to consider are how close you’ll get to other people and for how long.

“This virus really likes people being indoors in an enclosed space for prolonged periods of close face-to-face contact,” William Schaffner, an infectious-disease expert at Vanderbilt University, previously told Business Insider.

Other aspects to consider are how well ventilated an indoor space is, and whether patrons and staff members are wearing masks.

Here are six factors to think about when assessing how risky it is to go somewhere.

1. Is the activity you’re doing or the place you’re visiting indoors or outdoors?

A man wearing a mask runs in front of the Bay Bridge along the Embarcadero in San Francisco in April. Jeff Chiu / AP

The coronavirus typically spreads via droplets when people are close to someone sick for a while. Those types of prolonged interactions can happen anywhere, but experts have suggested that the risk of infection is lower outside.

A preliminary report from scientists in Japan (which has not been peer-reviewed) suggested that the odds that an infected person “transmitted COVID-19 in a closed environment was 18.7 times greater compared to an open-air environment.”

Another preprint of a study examined 318 outbreaks in China that involved three or more cases and found that all but one involved the virus jumping between people indoors. The case clusters studied, however, occurred while many people were under mandatory lockdowns, which might have skewed the results.

The reasons your chance of infection might be lower outside, Schaffner said, are that it’s easier to maintain social distance outdoors and that the virus has to navigate wind, heat, and humidity to jump between people.

People relax in marked social-distancing circles at Domino Park in the Williamsburg neighbourhood of Brooklyn, New York, on May 17. AP Photo/Kathy Willens

But that doesn’t mean people should congregate in the park or on the beach. No matter where you are, people should stay at least 6 feet apart.

“What you do becomes the single most important thing – less so the environment,” Schaffner said.

2. How well you can practice social distancing when doing an activity or visiting a certain place?

Kids swimming at a public pool. REUTERS/Lucas Jackson

Schaffner said the most important assessment he makes when deciding whether to enter a coffee shop, for example, is how well he can maintain his distance from other customers.

“I’m most concerned about how far apart I am from my fellow patrons,” he said, adding, “It continues to be prudent to keep as distant from people as possible, no matter where you are.”

3. If the place you’re visiting is indoors (like a restaurant or coffee shop), to what extent are patrons and staff members wearing masks?

Schaffner suggested being very careful in or near gatherings of any size – and “when in doubt,” he said, “don’t be stubborn, and wear a mask.”

Masks help protect other people from germs the wearer might be carrying, so they are imperative in situations where it’s difficult to maintain 6 feet of distance, he added.

“Make sure waitstaff are wearing gloves and masks,” Schaffner said. “If the waitstaff aren’t wearing masks, I’m getting my coffee across the street.”

4. Is the place you’re visiting well ventilated?

A masked cashier rings up purchases behind a plexiglass shield at a grocery store in Queens, New York, on April 3. Morse Collection/Gado/Getty Images

Scientists still aren’t certain to what degree a cloud of tiny coronavirus particles – known as aerosols – can linger in the air and infect the next person who walks through the space. But research has suggested that more live viral particles are found in the air in enclosed rooms with little airflow.

A study of two hospitals in Wuhan, China, found that the concentration of live coronavirus particles was highest in the air in nonventilated 9-square-foot toilet areas for patients, while the particles were less concentrated in the air in ventilated wards.

Some elevators, for example, could be transmission hot spots “if they are crowded and people ride in them for a long time, like a minute or more several times a day,” said Linsey Marr, an aerosol scientist at Virginia Tech.

Taped-off areas marking the suggested distance between people in an elevator of an office building in Singapore. Roslan Rahman/AFP via Getty Images

Schaffner agreed. “In such a tightly enclosed space without vigorous air movement for a short period of time, I’m afraid you might be exposed,” he said.

5. How long will you be visiting an indoor space?

People wearing face masks at a supermarket in Singapore on February 9. Ore Huiying/Getty Images

The worst coronavirus clusters around the US have been tied to places that force people into close quarters for extended periods.

The New York Times reported that all but one of the 12 hardest-hit US locations were prisons, jails, and meat-processing facilities. Nursing homes were also high on the list.

“The farther away you are and the shorter duration of contact between you and other people means you get less efficient virus transmission,” Schaffner said.

Offices and restaurants can also be risky for that reason.

A Cracker Barrel restaurant in Georgia that reopened after stay-at-home orders lifted in May. Courtesy of Cracker Barrel

In a letter recently published in the journal Emerging Infectious Diseases, scientists described how nine people sitting more than 3 feet apart at a restaurant in China got the coronavirus in January. The virus likely spread because of the restaurant’s air-conditioner, they said.

Similarly, an outbreak at a call centre in Seoul, South Korea, provided a case study of office transmission. Of the centre’s 811 employees, 97 got sick; all but three of the infected workers sat on the same floor, and 79 were in the same section.

6. Will you be able to avoid areas where people congregate for long periods?

People at California’s Newport Beach on April 27. Michael Heiman/Getty Images

People who play golf, go hiking, or visit the beach shouldn’t linger in locker rooms, at trailheads, or in parking lots, Schaffner said. That’s where people are more likely to stand around and have conversations without masks.

He suggested that people visit the beach for exercise rather than for tanning and relaxation.

“If you let people on a beach to exercise, they will stay apart,” he said. “If you let them bring beach umbrellas, they congregate and can’t keep their distance.”

“It’s people coming together in groups that matters,” Schaffner said.

Students at a graduation party at the University of Colorado Boulder on May 7. MediaNews Group/Boulder Daily Camera via Getty Images

A recent study found that talking loudly could produce enough droplets to transmit the coronavirus and that those droplets could linger in the air for at least eight minutes.

“Any gathering, from the point of view of the virus, is ideal,” Schaffner said. “People get together, exchange stories, and, thank you very much, the virus is going to go from me to you.”

That’s why fleeting encounters on a park trail are less risky.

A woman wearing a protective visor bikes through Paris on May 13. Samuel Boivin/NurPhoto/Getty Images

“I would not worry about walking by someone,” Dr. Amesh Adalja, an infectious-disease specialist at Johns Hopkins University,told Slate in late April. “Even in a healthcare setting, contact is defined by being near someone for a certain amount of time. I would not worry about these fleeting encounters.”

“The general principle should be: Outside is better than inside; open is better than closed; fewer is better than more people; and stay away from sick people,” Dr. Erich Anderer, a neurosurgeon and founding member of the North Brooklyn Runners group, told Insider.

A boy runs across a square in Stockholm, Sweden, on May 8. ONATHAN NACKSTRAND/AFP via Getty Images