COVID cases appear to be rising again in Colorado. Is another surge likely?
This story was originally published in The Colorado Sun.
Late last week, a key line on a chart monitoring coronavirus case trends turned red, signaling something public health experts had not quite anticipated to be happening so soon: COVID infections appear to be rising again in Colorado.
The increase so far is small, and it’s starting from one of the lowest levels of infection of the pandemic. It is not clear if the trend will be long-lasting or if the illnesses that occur during it will be severe, though there are reasons to think the answers to both questions are no.
But it is occurring as cases are also on the rise in other parts of the country and early warning signals from Europe are blaring. It is also happening as the state increasingly pulls back from its emergency response to the coronavirus — phasing out community testing sites that could provide a better sense of infection trends and changing hospital reporting requirements in a way that will provide less day-to-day visibility of the strain.
Here’s what we know so far.
Reported cases started rising again a week ago
On March 13, a Sunday, Colorado reported only 74 new coronavirus infections — the lowest daily total since the pandemic’s earliest days. But, since then, cases have been rising. By March 15, the state reported more than 400 new infections.
More significantly, the increase shows up in the state’s seven-day moving average of case counts, a key metric that smooths out the daily peaks and valleys. On the 13th, that average stood at about 186 new infections reported per day. By Thursday, the average had climbed to 250 new cases per day.
The change was the first time in more than a month that Colorado had seen an increase in cases. In the chart below, the line on the top shows that long declining trend that had, in recent weeks, flattened out.
The line on the bottom shows the daily direction of change. When the bottom line is green, it means cases are decreasing. When it is red, as it turned last week, it means cases are rising.
The trend is not entirely clear, though. The number of people in the hospital with COVID-19 has not increased, nor has the percentage of coronavirus tests coming back positive. Both of those numbers are used to confirm infection trends.
Monitoring of wastewater for the presence of the coronavirus has not shown a conclusive upward trend in Colorado.
(All of these numbers are up-to-date through Thursday. A systems error prevented the Colorado Department of Public Health and Environment from updating the figures on Friday, and the department usually does not update its data over the weekend.)
A new-ish variant is likely involved
One culprit for the apparent increases is a coronavirus variant that appears to be even more transmissible than omicron.
The variant is dubbed BA.2 — it hasn’t gotten its own Greek alphabet letter because it is technically considered a sublineage of the omicron variant, a cousin to the BA.1 omicron sublineage that tore through Colorado and the rest of the country early this year. Studies suggest that BA.2 is as much as 80% more transmissible than BA.1, which was more transmissible than the delta variant, which was more transmissible than the alpha variant, which was more transmissible than the coronavirus’ original form.
“Omicron was this super-infectious variant, and this is more infectious,” said Beth Carlton, a professor of epidemiology at the Colorado School of Public Health who is a member of the state’s COVID-19 Modeling Group.
As of the end of February — the most recent data available— BA.2 was estimated to account for about 7% of the new cases in the state, up from less than 1% at the beginning of the month.
Places across the country and world are also seeing a rebound in infections
Overall, reports of new infections continue to fall across the country. But in New York state, cases have risen by about 15% over the past two weeks. Officials in New York City estimate that BA.2 accounts for about 30% of the city’s new infections.
Meanwhile, wastewater systems across the country have begun picking up signals of rising coronavirus infections. Wastewater surveillance is seen as an important early-warning system for the country.
Most significantly, though, several European countries have recently seen new spikes in cases believed to be driven by BA.2. France, Germany, Italy and the United Kingdom are all in the midst of case surges, though those surges are still far below the spikes of their first omicron waves. Trends in Europe are often seen as harbingers of what’s to come in the United States.
The Netherlands also experienced a surge, but its cases are beginning to fall again.
If a new wave hits, it may not be as severe
Carlton said much remains unclear as modelers try to adjust their forecasts for the emergence of BA.2. But she said there’s reason for cautious optimism.
While the subvariant is more transmissible, it doesn’t appear to cause more severe illness and it also doesn’t appear any better at juking the immune system than omicron BA.1 was.
This means that people who are fully vaccinated and boosted will likely have protection against getting really sick. And people who caught COVID during the first omicron wave will likely have greater protection this time around. It could also mean a BA.2-driven wave would be a short one.
“Is this going to lead to a crushing wave like we had in January?” she asked. “Probably not because so many people were infected, and we have such high levels of protection.”
Carlton and others on the state’s modeling team estimate that about 90% of Colorado’s population currently has immunity to COVID — either through vaccination or prior infection. That still leaves more than 500,000 people susceptible, plenty for a surge caused by a highly infectious variant.
But Carlton said she does not believe such a surge would threaten hospital capacity. Instead, the challenge will be communicating to people how to assess risk for themselves.
“I think we’re out of the catastrophe phase,” she said. “But in this new phase, how do we inform people to make good decisions on how they protect their health?”
Colorado’s scaled-back approach may make it harder to understand a new wave
The state health department has announced that it will be winding down its large community testing and vaccination sites by the end of the month, as it hands off COVID services to traditional health care settings. The testing sites have been vitally important during previous surges, helping to confirm new infections.
The state has also ended its distribution of at-home rapid COVID tests.
And, last week, the state announced that hospitals will now report their numbers of COVID patients twice-weekly, with the hospitalization figures available to the public on the state’s website updated only once per week.
“This reporting cadence provides CDPHE sufficient data to track important COVID-19 trends over time during this stage of the COVID-19 response,” the agency wrote in a news release announcing the reporting change.
The changes in the state response show how much more responsibility individuals will need to take to protect themselves and the community during any coming infection surge. And Carlton said that won’t be easy — since some people, like those who are immunocompromised or live with someone who is — might remain vulnerable, while others can return to life as normal.
“I think that’s the hardest part of the current phase we’re in,” she said.