Colorado’s first confirmed case of the new omicron variant has been identified in a woman who recently traveled to southern Africa, the state Department of Public Health and Environment said Thursday. 

The woman, an Arapahoe County resident, has minor symptoms, was fully vaccinated and isolated at home, the agency said. She had not received her booster dose. She visited several countries in southern Africa, state epidemiologist Rachel Herlihy told reporters, and she wore a mask on her return travels late last week. She was not symptomatic until a day after she returned to Colorado via Denver International Airport, and she received a test the same day. That positive test was then flagged for sequencing by state monitors.

“This case was identified following a positive test result through routine case investigation by Tri-County Health Department, CDPHE’s epidemiologists flagged it for follow-up because of recent travel history,” the health department said. “CDPHE sent a team to collect an additional specimen for genome sequencing and has been working closely with Tri-County Health Department on case investigation.”

Colorado becomes the third U.S. state to confirm the virus’ presence. It was the first state to identify the alpha variant nearly a year ago, and the delta surge in Mesa County in late spring and early summer was an early warning of what that variant would bring to the state and nation.

Beth Carlton, an epidemiologist with the Colorado School of Public Health, said it was unsurprising that Colorado identified the case, given its high level of surveillance and its identity as a “highly connected state.”

The patient’s close contacts have tested negative. Gov. Jared Polis, in a news conference moments after the positive identification was announced, said he wasn’t “terribly alarmed.” The state uses random sequencing, about 15% of all positive tests statewide, to track for variants, and no other omicron cases have been identified yet. Nor has wastewater testing, a communitywide temperature check, revealed any infections.

“If community transmission is happening in Colorado, it’s very small,” he said.

The state is recommending any international travelers be tested within three to five days of returning, regardless of symptoms or known exposures. Herlihy said the state was also working with the Centers for Disease Control and Prevention to develop increased travel monitoring.  

Strategies used against delta will remain vital against omicron, Colorado officials say

The variant, which was circulating in Europe before it was officially identified in South Africa last month, has now spread across the globe and wound its way into the United States. Colorado officials have said it was a matter of when, not if, the strain appeared here. The tools used to fight previous variants – vaccinations, boosters, masking and distancing – will all remain at the center of the response to omicron, Herlihy said.

Much remains unknown about the variant, including whether it’s more transmissible than the standard viral strain or if it’s more severe. What’s known is that it has more than 30 mutations. Herlihy told reporters late last month that officials can infer from those mutations that the variant may be more transmissible and that reinfections of previously ill patients is a possibility. A “rapid increase” in cases in South Africa’s most populous province is another indicator that omicron may be more transmissible, she said Thursday.

Though many cases in South Africa have been reported to have mild symptoms, Herlihy said many of those cases were in younger people, who would fare better against the virus anyway. 

Polis said that more information should come in the next two to three weeks

It’s also unclear how omicron will interact with delta, the dominant variant in Colorado and the driving force behind the state’s months-long pandemic surge. Delta has accounted for nearly every new COVID-19 case here for months, state surveillance indicates, thanks to its high transmissibility. Whether omicron will overtake it, as delta did to a previous variant, or if the two strains will co-exist remains to be seen.

Omicron’s confirmed arrival here comes as the state battles a months-long surge and a multifaceted hospital capacity crisis. Though COVID-19 case and hospitalization numbers have improved of late, open beds remains tight, with both intensive and acute care capacity both exceeding 90% for weeks on end.