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Coronavirus

What do Colorado’s rising COVID cases mean for the summer?

State officials are trying to understand how the emergence of a new variant — omicron BA.2.12.1 — will impact the trajectory of infections

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Stop us if you’ve heard this one before during the pandemic: COVID cases are rising again in Colorado.

But what this means now — at a time when reports of new infections are still pretty low and the vast majority of the population has some kind of immunity against the virus — is a bit of an unknown that state health officials and researchers are still trying to understand.

Is this increase something to be worried about, akin to previous waves that killed thousands and tested the state’s hospital capacity? Or is this increase something more mundane, part of the new undulating rhythm that COVID will add to our everyday lives into the future?

Recent comments by the state’s top epidemiologist as well as new modeling projections from a team of public health researchers offer some insight. So here are answers to a few big questions.

How big of an increase are we talking about?

Right now, it’s small.

Over the past week, the state has been reporting about 640 new COVID cases per day. That’s up from around 300 new cases per day a month ago. But even at the higher number, Colorado is still seeing some of the pandemic’s lowest levels of transmission. At this time last year, the state was reporting around 1,600 new cases per day.

Seen on a graph of cases, the current increase looks like a little bump compared to the giant spike of this past winter. This suggests that another huge spike isn’t coming our way — at least not soon.

This chart, produced by the Colorado Department of Public Health and Environment, shows the 7-day average of new COVID-19 infections over time. The latest uptick in cases is just visible at the far right of the graph. Data are current as of April 21, 2022. (Provided by CDPHE)

“One thing that’s very different now from previous times in the pandemic is how low our levels of transmission are,” Dr. Rachel Herlihy, the state epidemiologist at the Colorado Department of Public Health and Environment, said. “There’s just very little transmission occurring right now. We wouldn’t expect the infections to grow rapidly without a significant shift in something.”

Weren’t we just talking about infections rising again?

Well, yeah.

Last month, CDPHE data showed an increase in cases over a two-week period. That increase turned out to be a data illusion, though. As the state processed a backlog of infection reports, the number of cases it counted earlier in March rose, wiping out the apparent increase.

This current increase appears solid, though. Herlihy said the state is now up to date on recording new infections. And there are other signs of an increase in infections.

Data collected from wastewater systems suggest an increase, as does “syndromic” data that measures the number of people showing up at hospital emergency rooms or at Kaiser Permanente primary care providers with COVID-like symptoms. The percentage of COVID tests coming back positive has also increased, now up to just over 5%.

The number of people who are hospitalized and positive for COVID has also nudged upward for the first time since January. As of last Wednesday — the most recent number available — 88 people were in the hospital with COVID in Colorado. That’s up 11 from the prior week, when the state recorded a pandemic-low 77 hospitalizations.

Should I be worried?

It depends!

The online news publication Vox has dubbed this the “choose-your-own-adventure phase of the pandemic.” In keeping with that idea, Herlihy said people’s individual circumstances will determine how concerned they should be.

“I think individuals really need to assess their own level of risk and the level of risk of their family members and contacts,” she said. “We know there continue to be lots of individuals in Colorado who continue to be susceptible to severe disease because of their underlying medical conditions.”

As Colorado Governor Jared Polis, left, listens, Dr. Rachel Herlihy, the state epidemiologist at the Colorado Department of Public Health and Environment, makes a point about the availability of COVID-19 vaccinations in the state during a news conference on the state’s efforts against the coronavirus Tuesday, April 27, 2021, in Denver.(AP Photo/David Zalubowski)

So, for some folks, any increase in infection prevalence is worrisome. But that won’t be true for everyone, especially this deep into the pandemic.

“We know going into this that we have a high degree of immunity in the state, from vaccinations largely but also from prior infections,” Herlihy said. “We know that immunity is even higher when it comes to severe disease.”

That immunity, she said, means the new case rise will be “hopefully just a blip.”

What does this mean for my summer plans?

Probably nothing, but we can’t say for sure right now.

To answer this question, it helps to understand what is believed to be behind the increase: another new variant.

Let’s call the variant of coronavirus that showed up in Colorado in March of 2020 original COVID. After that came the alpha variant — known scientifically as B.1.1.7. Then there was delta (B.1.617.2). Then omicron (the BA.1 version of B.1.1.529). Then the BA.2 subvariant of omicron. And now Colorado is seeing a rise in the proportion of cases caused by the BA.2.12.1 sub-subvariant of omicron.

Each of these variants has been more transmissible than the one that came before, leading them to rapidly replace the prior variant. After two months of accounting for nearly every new case of COVID in Colorado, the BA.1 version of omicron now makes up an estimated 18% of new infections. BA.2 accounts for about 70% of new infections, according to CDPHE surveillance numbers. And BA.2.12.1 makes up about 12% — up from less than 1% of new cases when it was first discovered in the state a month ago.

This chart, produced by the Colorado Department of Public Health and Environment, shows the change in the proportion of COVID-19 variants showing up in surveillance testing. The pink in the middle of the chart represents the delta variant. The green on the right side of the chart that rapidly replaced the delta variant is the omicron BA.1 variant. The yellow at the far right of the chart represents the omicron BA.2 variant, while the rising brown bars at the bottom right represent the BA.2.12.1 variant. Data are current as of April 25, 2022. (Provided by CDPHE)

So, if BA.2.12.1 is our immediate future, what do we know about it?

Herlihy said the variant is highly transmissible, but there is no evidence yet that it causes more severe illness or that it is any better than its omicron brethren at evading the immune system.

Last week, researchers with the Colorado COVID-19 Modeling Group released new projections for the future course of the pandemic. They estimated that about 1 of every 375 Coloradans is currently infectious with COVID and that immunity against the omicron variant stands somewhere around 90%. Immunity against severe illness — one bad enough to send someone to the hospital — was even higher, above 95%. (The modeling team also now takes into account access to anti-COVID drugs that can reduce the severity of illness when making its projections.)

This graph, included in an April 20, 2022, report by the Colorado COVID-19 Modeling Group, shows the growth in the estimated percentage of people immune to the omicron variant of COVID-19 over time. The yellow and orange lines at the top show immunity against severe infection for the whole population and for only the 65-and-older population, respectively. The blue and green lines at the bottom show the estimate for immunity from infection for both of those populations. (Screenshot by John Ingold, The Colorado Sun)

But … my summer plans? What’s going to happen?

Right, sorry.

The modeling group ran some projections for how many people will be hospitalized with COVID in the coming months depending on how much more infectious BA.2 omicron is compared with the original BA.1 omicron.

If BA.2 is 50% more transmissible and even if people continue dropping their personal COVID protective strategies, the team estimated that COVID would send about 700 people to the hospital at the wave’s peak in June. That’s not good, but it’s less than half of the hospital-straining numbers seen during the delta and earlier omicron waves.

The team also looked at what might happen if a new variant arrives on the scene, drawing up estimates based on whether the variant is more infectious, more severe or more immune-resistant than omicron. In this model, hospitalizations don’t exceed prior peaks unless the variant can hit the trifecta of higher transmissibility, severity and immune-escape ability.

“What they are projecting in really most of the scenarios is hospitalization numbers that don’t come close to what we saw with thh omicron surge,” Herlihy said.

So, if these projections hold, that means your summer plans will probably hold, as well. But this advice comes with the usual pandemic caveat: No one knows what surprises await.

“Unfortunately, I don’t have a crystal ball,” Herlihy said. “I don’t know for sure.”


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