That “killer cardio” class at the gym might take on a new meaning for people worried about the new coronavirus.

Exercise is a prescription for good health, but is it wise to visit a health club as the outbreak grows?

Some cities and states — including Los Angeles, San Francisco, New York, New Jersey and Connecticut — have already decided that question for its residents, ordering gyms to close to maximize social distancing and help stop the spread of the virus.

Some national fitness chains, including LA Fitness, have temporarily shuttered all U.S. locations. Gold's Gym has closed all company-owned U.S. clubs, including gyms across Texas, Oklahoma, St. Louis, Alabama, the Carolinas, Colorado Springs and Venice, California.

On March 16, the Coronavirus Task Force urged Americans to avoid gathering in groups of more than 10 people, effectively shutting down group fitness classes.

What about places where gyms are still open?

When it comes to healthy younger people who have no symptoms and live in areas where there’s no widespread disease, it’s safe to go to the gym, said Dr. Michael Ison, an infectious disease physician at Northwestern Medicine in Chicago.

“But they have to use extra care,” Ison told TODAY.

“You have lots of people coming and using shared equipment. When you work out, you often are rubbing your face and nose to get the sweat off and then touching the handlebars — that would be a great way for someone to potentially share the virus.”

Whether it’s safe to go to the gym may change over time as more cases emerge. It’s also important to follow local guidance since the outbreak is worse in some areas than others.

The more important question may be: Should you go to the gym even if it seems safe? There's a generational call for healthy younger people to stay at home to prevent the outbreak from growing worse.

People who are at-risk for complications from COVID-19 — older adults over 60 and patients with underlying medical conditions — should minimize their exposures to the public, which would include skipping the gym, Ison noted. His father, who is in his 80s, has stopped going to his health club to protect himself.

For those who want to keep the maximum social distance, the safest way to exercise may be in a home gym.

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People who do decide to go to a health club should be very diligent about washing their hands both before and after they work out, Ison noted.

Here’s more advice for healthy young people in areas without a widespread outbreak:

Using cardio or weight machines:

Be sure to wipe down the machine thoroughly with an anti-bacterial wipe before and after you use the equipment — a dry towel or a towel with water won’t do the trick, Ison said. Try to disinfect all surfaces. Keep your distance from other people.

Taking a group class:

The number of people in an aerobics class is relatively small and there’s usually a reasonable degree of separation between the participants, Ison said. But again, the Coronavirus Task Force is now urging Americans to avoid gathering in groups of more than 10 people, so group fitness is coming to a halt.

Use your own mat in a yoga class. If using a mat provided by the health club, clean it with antimicrobial wipe.

Swimming in a pool:

The chlorine in the pool will likely inactivate the virus, so doing laps is probably less of a concern, Ison said.

“The bigger issue is that you have to change in the shared locker rooms, and people are often touching the mouth, nose and face and then maybe touching the lockers,” he noted.

“If you do, wash your hands carefully before and after swimming in the pool.”

Running outside:

This seems to be the best bet. Sunlight is “nature’s greatest disinfectant” because the ultraviolet light inactivates bacteria and viruses, said Joseph Fair, a virologist, epidemiologist and NBC News Science contributor.

When exercising outside, there are also fewer people close enough to you for their respiratory droplets to reach your body when they sneeze or cough.

The city of San Francisco, which has ordered residents to stay at home until April 7 except for essential needs, is allowing outdoor activities, such as walking, hiking or running, as long as people maintain at least 6 feet of social distancing.

Other everyday activities:

Going to a restaurant or cafe: Some cities and states have ordered eateries to shut down, except for takeout and delivery. In places where restaurants are still open, it’s generally safe to go out to eat, Ison said. The cooking process will inactivate the virus. But if there’s someone sick sitting next to you or working at the eatery, ask to move or don’t eat at that establishment. Don't go in a big group since the Coronavirus Task Force is urging Americans to avoid gathering in groups of more than 10 people.

Getting a haircut: That’s slightly lower risk because it’s just you and the hairdresser, Ison said. But stay away from sick clients and wash your hands after touching anything in the waiting area. “If the barber is sick, I probably wouldn’t get my hair cut that day,” he noted.

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