Denver has extended its indoor mask order, the city announced Tuesday morning, as omicron surges through the metro area and the state.

Denver’s order, initially set to expire next week, will now run through Feb. 3, the city’s Department of Public Health and Environment announced Tuesday morning.

Businesses in Denver can still apply to go mask-free if at least 95% of staff and patrons are fully vaccinated. The order was implemented just before Thanksgiving, as hospitals filled up across the state.

That wave had subsided steadily through much of December, and Denver’s average positivity rate “dropped to below 5%,” the city wrote in its announcement Tuesday. But the rapid emergence of omicron, the latest, highly transmissible variant, has reversed gains made in infection rates.

“In November, Denver and much of the metro area took the necessary steps to curb the rising spread of COVID-19 and reduce the dangerous pressure on our hospital systems. Our efforts were not in vain,” Denver Mayor Michael B. Hancock said in a statement. “As the Omicron variant continues to spread during this holiday season, and hospital capacity remains strained, we simply cannot afford to let up now.”

Bob McDonald, the executive director of the Denver health department, said in an interview that the decision to extend the order was made in the past few days, in conjunction with other area health departments. He said the city was not considering any other public health measures.

“As long as we have a very infectious variant that’s driving case rates up, it would be irresponsible to lift a face-covering order right now,” he said. He stressed that vaccines – and boosters in particular – are still effective at protecting against severe disease and illness. As of Tuesday morning, 80% of COVID-19 hospital patients in Colorado were unvaccinated.

More than 13.5% of COVID-19 tests in Denver have returned positive over the past week, according to city data. On Dec. 14, Denver’s one-week incident rate was 184.7 cases per 100,000 residents. As of Tuesday, it had shot up to 565.7. McDonald said case rates are the highest they’ve been in a year.

The past 21 months have shown the impossibility of predicting the virus, he added, but his “sense is that (omicron is) going to go through the community very, very quickly, and then it’ll drop very, very quickly.”

“I think the worst is yet to come,” McDonald continued. “But then once we see that peak, my sense is, especially going into springtime, my sense is that it’ll go down quickly.”

J. J. Ament, the president and CEO of the Denver Metro Chamber of Commerce, said in a statement that he supported local decision-making. But he said businesses should receive “adequate resources” and be shielded from sanctions and fines.

“Data shows that wearing masks alone will not do the job of protecting ourselves and our community,” he said. “The best defense against serious illness from COVID-19 is getting vaccinated and boosted, so we and our members are encouraging everyone to do so.”

Other counties in the area with mask orders – Boulder, Broomfield, Adams, Jefferson and Arapahoe – are also continuing their orders, according to the Denver health department and a news release from the Colorado Health Institute. Boulder has had a face-covering order for months; Broomfield’s requirement applies only to city- and county-owned buildings; and Jefferson’s order is pegged to certain pandemic metrics made far more difficult to achieve because of omicron.

Adams and Arapahoe counties, under the umbrella of the Tri-County Health Department, also extended its mask order, a spokeswoman for the agency said.

With the exception of Boulder, whose order predated the rest of the area by nearly three months, those metro counties all moved in near-lockstep last month to institute face-covering orders. They had urged Gov. Jared Polis to mandate masks statewide, and when he refused, they did so together.

“Wearing masks indoors slows the spread of respiratory viruses,” Dawn Comstock, the executive director of Jefferson County Public Health, said in a statement. “Last month’s COVID-19 surge was reduced because people in our communities wore masks and got vaccinated, including booster doses. Continuing these strategies will save lives as we experience the rapid growth of the omicron variant as well as increasing influenza cases. We cannot become complacent.”

The counties instituted their mask orders in large part to help prop up hospitals, which were teetering amid a crush of COVID-19 patients, staffing shortages and sicker patients overall. While that pressure has alleviated somewhat after the orders were put into place, omicron brings a new threat, McDonald said.

“Hospitals are certainly at risk, perhaps more than ever, and it’s not just because omicron is very infectious,” he said. “It’s that hospital staff are being infected, too.”

Even though hospital workers are required to be vaccinated, and so their cases are likely to be more mild, they are still required to isolate if infected, he said. That’s going to further stretch an already thin workforce.