Omicron variant found in 21 Colorado wastewater systems, making up ‘potentially half’ of new cases

By: - December 22, 2021 3:57 pm

Dr. Rachel Herligy, state epidemiologist for Colorado, speaks during a news briefing about the state’s response to COVID-19 on April 20, 2021. (Governor Jared Polis Facebook)

The omicron variant has now been found in every wastewater system that participates in Colorado’s detection system and is connected to nearly half of all new COVID-19 cases in the state this week, health officials said Wednesday. 

“At this point, we do believe that omicron is widespread across the state and there is likely local transmission occurring in many of our communities, if not most of our communities, now,” state epidemiologist Rachel Herlihy said during a media update. 

Of the positive PCR tests analyzed in the state’s laboratory, approximately 45% have the omicron variant’s identifying S-gene dropout. For comparison, it showed up on less than half of the tests from Dec. 12.


“We could infer that potentially half of what we’re seeing in the state, at least as of a couple of days ago, is potentially the omicron variant,” Herlihy said.

Herlihy said the rapid increase in omicron cases shows the variant’s significant transmissibility. The odds of a close contact becoming infected is twice as high with omicron than it is with the delta variant. 

The state is seeing more reinfection and breakthrough cases with omicron, and Herlihy echoed advice from Gov. Jared Polis that three doses of the COVID-19 vaccine provide the most protection.

While the data on omicron’s severity is not clear yet, Herlihy said that the new variant could still threaten Colorado’s hospital capacity. The state’s COVID-19 cases have begun an upward tick in the last few days, but there is a continuing decrease in the number of hospitalizations due to COVID-19.

“It’s a variable picture on what severity might look like,” she said. “But a lot of the messaging we’re hearing from other countries and from our federal partners is that even if we see less severity, the increased number of cases … may be enough to increase hospitalization rates substantially.”

As of Dec. 22, there were 1,026 people hospitalized with COVID-19 in Colorado.

On Wednesday, the Eagle County Board of Health became the latest local government to reinstate a countywide mask mandate in response to a dramatic spike of COVID-19 cases. The county’s case rate was previously at about 300 cases per 100,000 people but skyrocketed to 1,000 cases per 100,000 people as of Wednesday, the board wrote in a press release

“Officials theorize the spike is due to the rise of the highly transmissible omicron variant in the community, as well as a large number of visitors present during the holidays,” the release reads.

Eagle County’s mask mandate will be in effect until at least Jan. 17. Most counties in the Denver metro area have also reinstated indoor mask orders.


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Sara Wilson
Sara Wilson

Sara Wilson covers state government, Colorado's congressional delegation, energy and other stories for Newsline. She formerly was a reporter for The Pueblo Chieftain, where she covered politics and government in southern Colorado. Wilson earned a master's degree in journalism from Northwestern University, and as a student she reported on Congress and other federal beats in Washington, D.C.