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What's My Risk of COVID?

photo of grocery shopping

Nov. 9, 2020 -- As the coronavirus pandemic begins its ninth month and the number of COVID-19 cases in the U.S. tops10 million, it's human nature to wonder: What is my risk of getting infected?

And the answer is far from simple.

"An individual's chance depends heavily upon their location and their risk factors, such as age and occupation, and upon the unpredictable future course of the pandemic," says Natalie E. Dean, PhD, an assistant professor of biostatistics at the University of Florida in Gainesville. And the future course, she says, depends on whether new restrictions will be added or relaxed and other factors. "So it is a complex question."

It's a bit easier to answer the question when it is more specific, says Susan Holmes, PhD, a professor of statistics at Stanford University. Look at infection rates in your area to help find out how risky it might be to go shopping or use public transportation.

"Right now, the risk of contracting COVID is different in Wisconsin than in California, so each of these probabilities is a function of the prevalence of contagious people in your neighborhood, locations you visit, and how protected you and others are with masks, ventilation, physical distancing."

Using Risk Calculators

A variety of calculators and other tools can help predict individual risk -- or how risky the situation or event is. Here is a sampling.

Risk of contact with an infected person: Researchers at the Georgia Institute of Technology and Stanford University worked together to develop a tool that estimates how likely it is that at least one person at any event of a given size in a specific location is infectious.

"We are trying to communicate the risk of potential exposure," says Joshua S. Weitz, PhD, a Patton distinguished professor of biological sciences at the Georgia Institute of Technology.

Taking the size of the event into account, the risk level is the estimated chance, from zero to 100%, that at least one person present will be COVID-19-positive. The researchers assumed there are usually 10 times more cases than are being reported, although that may drop to five times in regions that have more testing.

For instance, on Nov. 5, the chance that at least one person is infected at a 50-person gathering in Los Angeles was 69%; when that gathering was limited to 15 people, the risk was 29%.

Being in contact with someone infected, Weitz says, ''is just the first step in a chain of transmission." Among the other things that affect your risk, of course, is whether the event is inside or outside, and the level of protection such as wearing masks and social distancing.

Risk of infection while traveling: Holmes of Stanford suggests turning to CDC information to assess specific risks of contracting COVID-19 during travel.

For instance, short trips by car with members of your household only and no stops are lowest-risk; flights with layovers are among the highest-risk ways to travel. Vacation rentals with household members only is lower-risk than bed-and-breakfast lodgings. Dormitory-style hostels are highest-risk.

Personalized COVID risk tool: Experts from Brown University and Lifespan developed a tool called My COVID Risk. It assesses risk when taking part in everyday activities, ranking risk from low to high.

For instance, going to an indoor gym near Los Angeles with 20 people present for an hour, all wearing masks, carries a medium risk of infection. Reducing the time to a half-hour, with five people, all masked, makes the activity low-risk.

Taking a 1-hour walk outdoors in Boston with five people, all masked, is very low-risk.

"There is not just one answer," says Weitz. "Think about risk across a spectrum.”

WebMD Health News

Sources

Susan Holmes, PhD, professor of statistics, Stanford University, Stanford, CA.

Joshua S. Weitz, PhD, Patton distinguished professor of biological sciences, Georgia Institute of Technology, Atlanta.

Natalie E. Dean, PhD, assistant professor of biostatistics, University of Florida, Gainesville.

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