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This artificially colorized image shows a cell infected with the omicron variant of the SARS-CoV-2 virus, which causes COVID-19. (Provided by the National Institute of Allergy and Infectious Diseases)

So, once upon a time, several years ago now, there was just COVID-19 — or more accurately, SARS-CoV-2, the virus that causes COVID.

Then the virus started mutating and spitting out variants. The alpha variant was surpassed by the delta variant, which was surpassed by the omicron variant, which then gave birth to a whole mess of new variants that competed against each other like so many one-upping Williams and Harrys.

And now comes XBB.1.5, heir to the omicron throne, possessor of the nickname “Kraken”, conqueror of the Northeast, perhaps the most transmissible variant of SARS-CoV-2 to date.

But you didn’t come here for a lesson in lineage. You want to know if you need to care. And the answer, according to two Colorado epidemiologists is: Maybe. Probably. But whatever comes our way also likely won’t be as bad as what has come before.

What is XBB.1.5 or the “Kraken” COVID variant?

The new COVID variant is a born-in-the-USA chimera known as a “recombinant” variant. It descended from a variant that was created when two other variants infected one person at the same time and then mixed and matched their genes to form a new variant.

Its transmissibility edge appears to come from a better-than-usual ability to bind to receptors on our cells, said Dr. Rachel Herlihy, the state epidemiologist at the Colorado Department of Public Health and Environment.

“It does look like it spreads more easily from person to person,” she said.

The variant was first identified in October in New York. Since then, it has come to dominate transmission on the East Coast.

According to projections from the Centers for Disease Control and Prevention, the variant accounts for more than a quarter of the new cases nationwide but more than 70% of new cases in New England, New York and New Jersey.

In the mountain West, the variant is so far more subdued. For the region that includes Colorado, as well as Montana, North Dakota, South Dakota, Utah and Wyoming, XBB.1.5 accounts for an estimated 6.6% of new cases, while its parent variant, XBB, accounts for another 4.4%.

Julianna Sandoval, 24, pauses for a COVID-19 nasal swab test from Dr. Sarah Rowan from Denver Health Medical Center. Rowan and other medical staff administered a free drive-up COVID-19 testing in the parking lot of Abraham Lincoln High School on November 7, 2020. (Kathryn Scott, Special to The Colorado Sun)

Still, we’ve seen this story before in Colorado. Variants that start on the East Coast often work their way inland — meaning Colorado should expect to see XBB.1.5 hit harder at some point.

“It’s not evenly distributed across the U.S.,” said Beth Carlton, a professor of epidemiology at the Colorado School of Public Health. “It’s grown very rapidly in the Northeast, and there’s every reason to think it will do the same when it gets here.”

What has kept the Kraken at bay so far?

And yet, here we are in January — three months since the variant was discovered — and XBB.1.5 hasn’t yet made much of a dent in Colorado. Both Carlton and Herlihy said the reason may have to do with timing.

There is by now a pretty well-documented seasonality to COVID infections. They are more likely in colder months, less likely in warmer months. But Colorado is a bit unique nationally in that, for reasons yet unknown, our cold-weather COVID waves often peak earlier — around the end of November or beginning of December.

That’s what happened this season when a small wave of cases peaked in November and has been declining ever since. The wave was largely driven by different omicron-descended variants — BA.5, BQ.1 and BQ.1.1. (This story provides a pretty good rundown of why new COVID variants all sound like they were christened by someone flipping through a baby name book written by Elon Musk.)

Carlton and Herlihy said having that wave come before the arrival of XBB.1.5 might have given the state a little immunity boost.

“Perhaps there was some added immune protection because of that recent wave which could be resulting in a slower introduction of XBB,” Herlihy said.

Will the new variant overwhelm hospitals?

Any new wave of cases would bring risks. Every infection comes with the risk of long COVID symptoms. People who are more vulnerable to severe illness — those who are older and those who have weakened immune systems — would be at higher risk of being hospitalized or dying if they got sick.

But Herlihy said she does not foresee a wave of illness from XBB.1.5 that would overwhelm the state’s hospitals.

While more transmissible, the variant has not yet shown to be more virulent — that is, there’s no evidence so far that it makes people sicker than other omicron variants. With an overwhelming percentage of the population in Colorado having some kind of immunity to the virus, whether through prior infection, vaccination or both, that means there will likely be fewer severe illnesses from an XBB.1.5 wave than during earlier COVID waves.

“At this point, at least due to COVID alone, we are feeling optimistic that we have the health care capacity,” Herlihy said. “Of course the wild card is the consideration of multiple viral pathogens.”

By “multiple viral pathogens,” Herlihy is referring to two other respiratory illnesses that have hit Colorado hard this winter: flu and RSV. Both are now trending downward — hospitalizations for the flu briefly outpaced hospitalizations for COVID late last year but have now fallen below.

But Carlton said it’s not uncommon for flu infections to have a late-season resurgence. If that happened at the same time there was a new wave of COVID cases, it could put hospitals under stress.

“It’s a good reminder that the flu vaccine is still something worth getting,” Carlton said.

Your XBB playbook: Test, rest, address

OK, so how should you handle a potential XBB.1.5 wave? Carlton has a three-step plan.

First: Test. If you think you might be sick, take a COVID test to know what you have. The federal government late last year reopened its program for people to order free at-home tests.

Second: If you are sick — with anything — stay home. Don’t risk spreading whatever it is you have.

And third: Take the steps necessary to protect yourself.

Are you at greater risk of developing a bad case of COVID? It’s probably time to start wearing a mask again in public, if you haven’t been already. Herlihy said, even if those around you aren’t masked, a quality, tight-fitting mask will provide the wearer some protection.

Haven’t yet received an updated COVID booster shot? Schedule one now. Since XBB.1.5 is an omicron spawn, an updated booster will give you a defense against severe illness.

Did you get COVID — especially if you are in a higher-risk category? Ask a doctor about receiving Paxlovid, the COVID antiviral drug that experts believe is effective against XBB.1.5. Starting the antiviral treatment early will cut your risk of getting really sick.

Carlton said this is the COVID playbook — one that is as useful for XBB as it will be for any future variants that emerge.

“These,” she said, “seem like three basic principles to move forward with.”

John Ingold

John Ingold is a co-founder of The Colorado Sun and a reporter currently specializing in health care coverage. Born and raised in Colorado Springs, John spent 18 years working at The Denver Post. Prior to that, he held internships at the Rocky Ford Daily Gazette, the Colorado Springs...