How XBB.1.5 variant will impact Colorado remains unclear as COVID hospitalizations continue to drop

Colorado’s COVID-19 numbers continued to improve this week, but it’s still not clear whether the latest variant could send new infections and hospitalizations up again.

When the delta and omicron variants first arrived in the country, they drove up hospitalizations and deaths everywhere in a relatively short time, though highly-vaccinated populations weren’t hit quite as hard.

Now, it’s more difficult to predict whether a subvariant like XBB.1.5, which has pushed hospitalizations up in the Northeast, will do the same in Colorado, said Talia Quandelacy, an assistant professor of epidemiology at the Colorado School of Public Health.

Regardless, it’s a good idea to get a booster shot to reduce your odds of severe illness, if you haven’t had one recently, Quandelacy said. People who want to reduce their odds of getting sick can also wear masks in crowded indoor spaces, she said.

Colorado’s COVID-19 hospitalizations continued to drop this week. As of Tuesday afternoon, 196 people were hospitalized statewide with the virus, down from 245 a week earlier.

The other numbers also were moving in the right direction. Viral concentrations in wastewater were decreasing in 32 utilities’ watersheds, increasing in seven and stable in 19. About 7.4% of tests came back positive over the last seven days, down slightly from 7.9% a week earlier, and the number of new cases dropped by about 400, with 2,721 recorded in the week ending Sunday.

“It looks like most of the indicators are starting to go down,” Quandelacy said.

The Centers for Disease Control and Prevention didn’t consider any Colorado counties high-risk, based on hospitalizations and cases. More than two-thirds of counties had “substantial” or “high” transmission, though, based on cases and the percentage of tests coming back positive.

Nationwide, COVID-19 hospitalizations are dropping again, according to data compiled by The New York Times. They had risen in the Northeast as XBB.1.5 displaced BQ.1 and BQ.1.1 as the dominant variant.

The CDC estimated XBB.1.5 accounts for about 15% of infections in the region including Colorado, which is lower than the national average of 43%. While XBB.1.5 appears to be more contagious and better at evading the immune system than previous versions of omicron, it’s not a given that hospitalizations will tick up in Colorado as they did in the Northeast when it takes over, Quandelacy said.

Multiple subvariants of omicron were circulating at different levels in different parts of the country, Quandelacy said. It’s likely that someone who was recently infected with one will have some cross-protection against others, but it’s not clear how much protection each would offer, and public health officials only have a rough idea of how widespread any given version of the virus may have been, she said.

“Part of what is happening now is that we’re seeing these variants from the same family,” she said. “There’s different pockets of the population that have been infected by these different subvariants.”

The Colorado Department of Public Health and Environment didn’t post updated data on flu and respiratory syncytial virus Wednesday, as state offices were closed due to the snowstorm. Hospitalizations for both were trending down last week, and the CDC downgraded Colorado’s level of flu-like illness from “very high” to “high” on Friday.

Seasonal flu activity is declining in most parts of the country, according to the CDC. Still, about 12,000 people were hospitalized with flu in the last week, bringing the estimated total to 260,000 hospitalizations and 16,000 deaths nationwide.

RSV appears to be behaving as it normally would, with a winter peak and a sustained drop afterward, Quandelacy said. With flu, it’s harder to tell if it will continue decreasing, like it would in a typical year, or have a second peak as it did last spring, she said.

“This has been an atypical season,” she said.

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