Kaiser Health News points out that gym customers “moving around indoors, sharing equipment and air, and breathing heavily could be a recipe for easy viral spread.” Gym owners say the notion of their facilities being coronavirus hotspots is overblown.

A industry-sponsored study released in September claimed that it’s safe to work out at gyms and that no evidence has emerged tying gyms to the spread of the coronavirus.

Emily Landon, chief infectious disease epidemiologist at University of Chicago Medicine, disagrees with that proclamation.

“It certainly isn’t a blanket statement that all gyms are safe,” Landon told The Washington Post. “Gyms may be safe. Gyms may not be safe. This study doesn’t answer that question.”

Healthline notes that warm, moist air combined with turbulent air flow from exercising might create an environment where virus droplets can easily spread. The website highlights a South Korean study that warns against rigorous exercise in confined places like fitness centers.

“When people breathe more rapidly and more deeply, they expel greater numbers of droplets,” Dr. Robert Glatter, an emergency medicine physician at Lenox Hill Hospital in New York City, told Healthline.

However, a randomized study of 3,764 individuals initiated by Norwegian researchers in late May, after the country’s gyms opened with social distancing measures (one meter of distance required for floors exercises and two meters of distance required for high-intensity classes; locker rooms remained open while showers and saunas were off limits) found no significant COVID-19 infection risk as long as health guidelines were followed. Norway, Germany and Austria also did not trace significant outbreaks of COVID-19 to gyms in general after gyms were allowed to reopen with precautions in Northern Europe.

A study released in September by the U.S. Centers for Disease Control and Prevention (CDC) found that people who tested positive for the coronavirus were twice as likely as those who hadn’t tested positive to have dined at a restaurant recently.

“Exposures and activities where mask use and social distancing are difficult to maintain, including going to places that offer on-site eating or drinking, might be important risk factors for acquiring COVID-19,” the CDC says.

Reports of coronavirus exposure inside of restaurants have been linked to air circulation, according to the CDC.

“Direction, ventilation and intensity of airflow might affect virus transmission, even if social distancing measures and mask use are implemented according to current guidance,” authors of the CDC study wrote. “Masks cannot be effectively worn while eating and drinking, whereas shopping and numerous other indoor activities do not preclude mask use.”

The Texas Restaurant Association takes issue with the study, saying the data is flawed. The trade group notes that statewide safety protocols are preventing the spread of the coronavirus in Texas restaurants.

“It is irresponsible to pin the spread of COVID-19 on a single industry,” the association says.

Because dozens if not hundreds of people congregate at religoius facilities, health experts say they can easily become virus-spreading venues. For instance, the CDC reported that 38 percent of the 92 attendees at an Arkansas church contracted the coronavirus in early March, and three of them died. Another 26 cases in the community, including one death, were linked to the church.

Since frequency and volume of talking can also play a role in spreading the virus, houses of worship where people are singing or praying aloud, are also higher risk, especially since many religoius structures are older buildings with worse circulation than modern facilities. 

In July, The New York Times reported that more than 650 coronavirus cases in the U.S. had been connected to churches and religious events since the outset of the pandemic.

“There’s a very fine line between protecting the health and safety of people, and protecting the right to worship,” George Murdock, a county commissioner in Oregon, told The Times.

Milne emphasizes that movie theaters are windowless places where customers sit in close proximity to strangers for a two to three hours at a time. Thus, they can be breeding grounds for the coronavirus.

“It’s exactly the type of scenario we need to be avoiding to reduce opportunity for the virus to spread,” Anne Rimoin, professor of epidemiology at the UCLA Fielding School of Public Health, told Health.

Health notes that mask-wearing and social-distancing guidelines vary by theater and location.

“There is no zero-risk scenario going to a theater,” Rimoin says, “and we should be doing everything we can to either bring down or keep down rates of transmission.”

There is some evidence that volume of talking also plays a role in COVID-19 infections. Therefore a movie theater, where patrons are sitting quietly and mostly masked, is less risky than restaurants and bars where people are often sitting unmasked and talking loudly. 

Despite the many coronavirus precautions that hair salons, nail salons and barbershops have undertaken, health experts remain nervous about visiting them. Why? Because workers and customers, regardless of whether they’re wearing masks, are in such close contact with one other.

“If you are in a close physical space with other people for a longer period of time, your risk of exposure becomes greater,” Dr. Sandra Kesh, an infectious disease specialist and deputy medical director at Westmed Medical Group in Purchase, N.Y., told Healthline.

“If you’re passing by someone quickly like you might on the sidewalk or a bike path, for instance, the risk of getting coronavirus is smaller than being within 1 or 2 feet of someone washing your hair and giving you a haircut for an hour or more.”

However, similar to gyms, the risk of infection at hair salons is also tied to density and following advised safety precautions. A case of a hair salon in Springfield, Mo. has become one of the most high-profile examples of how much of a difference following health guidelines can make. While two of the hairdressers at the salon tested positive for COVID-19 back in May, none of the 139 salon clients they interacted with became infected.

The likely reason? Both hairdressers wore face coverings and the salon was operating at 25 percent of capacity.

A number of coronavirus outbreaks have hit factories and warehouses across the country. And it’s no wonder, since employees are often packed into relatively tight quarters.

In response to outbreaks, some factories and warehouses have been forced to shut down, while others have reconfigured their spaces to accommodate social distancing.

According to a study conducted by Amazon of 1.327 million front-line Amazon and Whole Foods employees who worked for the company from March 1 through Sept. 19, 19,816 of its workers either tested positive for COVID-19 or were presumed to have had it.

Amazon claims that rate of infection is actually lower than the rate of infection for the general U.S. population by 42 percent, based on data collected by John Hopkins University on U.S. infections as a whole during the same period.

Given the lack of fresh air and the challenges of social distancing, many state and local governments have severely limited crowd sizes at indoor stadiums. In a poll taken in June by the University of Texas/Texas Politics Project, 79 percent of Texans said they thought it was unsafe to attend a sporting event or concert at an indoor arena. Only 21 percent thought it was safe to do so.

“Though the billions of dollars that have been spent over the last 25 years to upgrade sports facilities across the country have made high-efficiency air filtration systems more common, more will likely need to be spent on these state-of-the-art systems to make fans feel safe in the post-coronavirus era,” according to the InsideHook sports website.

The CDC says outdoor activities are safer than indoor activities when it comes to guarding against the coronavirus. A study done early during the outbreak, in China, found that out of 7,324 infection cases, just one could reliably be traced to an outdoor transmission, to a man who had a conversation outside with someone experiencing the early onset of COVID-19. The reason is that viral particles are likely to be diluted much more quickly in the large volume of air outdoors. In fact, 80 percent of the outbreaks tracked in that study were traced back to people living in the same household (indoor transmission), while other venues accounted for 20 percent of transmissions.

Still, the virus can spread at outdoor event venues, particularly if they involve a big, densely packed crowd.

Whether indoors or outdoors, stadiums “are more problematic from a virus perspective because it means a lot of noses and mouths close to other noses and mouths. Often, those settings are emotional, physical and can include alcohol,” Minneapolis TV station WCCO says.