Throughout the COVID pandemic, it's become increasingly clear that certain types of businesses in particular can pose a serious COVID risk: those that are indoors with poor ventilation where people tend to gather close together. And while most states have now reopened the majority of businesses, Anthony Fauci, MD, the nation's leading immunologist, is warning that three specific businesses should stay closed amid COVID.During an appearance on MSNBC's All In on Sept. 17, host Chris Hayes pointed out that Arizona, Texas, and New York benefitted from closing certain establishments. And Fauci said, "I totally agree" with that tactic."In fact, the CDC just came out—if you go on their website—with a figure that's really telling. It shows the odds of risk of different types of situations that give you a higher risk of transmissibility," he explained. The CDC study Fauci was referencing examined COVID cases across 11 U.S. health care facilities and looked at the ratio of patients who received negative versus positive COVID test results and where they'd been in the past two weeks. Read on to find out the three businesses that create the most COVID risk, according to the CDC and Fauci. And for more risky behavior to avoid, check out 24 Things You're Doing Every Day That Put You at COVID Risk. 1 GymsFauci pointed out that one of the three riskiest places to go are gyms, where people tend to breathe heavily, expelling more potentially contaminated droplets, and where there isn't outdoor air filtering in.Among the patients studied by the CDC, 7.8 percent of people who tested positive had been to the gym in the past two weeks, while just 6.3 percent of those who tested negative had. And for more on COVID and gyms, check out This Is The Absolute Worst Place to Go in Your Gym During Coronavirus. 2 Bars"You've gotta look very carefully at things like bars, [which] are a really important place of spreading of infection. There's no doubt about that," Fauci told Hayes. "And that becomes particularly important if you happen to be in an area where there's a high degree of community spread."In the CDC study, 8.5 percent of people whose tests came back positive had been to a bar in the two weeks prior, compared to 5 percent of patients with negative test results. 3 RestaurantsThe CDC found that the biggest disparity between where positive COVID patients had gone versus negative COVID patients was restaurants: 40.9 percent of patients with COVID had dined out two weeks prior compared to just 27.7 percent of those who tested negative."When you have restaurants indoors in a situation where you have a high degree of infection in the community, you're not wearing masks, that's a problem," Fauci said. "So those are things that are crystal clear." And for more COVID updates, sign up for our daily newsletter. 4 Religious gatheringsWhile Fauci didn't call these out himself, the CDC report he referenced noted a marked different between the percent of people with positive COVID tests that had gone to church or another religious gathering (7.8 percent) and the percent of people with negative COVID tests that had (5 percent). And for more on this study, check out These Are the 4 Places People Went Before They Got COVID, Study Says.