"Kraken" COVID variant XBB.1.5 has achieved projected dominance in the U.S., comprising an estimated 43% of cases this week, according to an updated forecast from the U.S. Centers of Disease Control and Prevention released Friday.

BQ.1.1, also known as Cerberus, came in second, fueling an estimated 29% of cases. It was dominant last week. BQ.1, Cerberus’ parent variant, came in third, at an estimated 16%. All other variants were projected to comprise 3.9% or less of cases.

As Kraken continued on its warpath this week, U.S. COVID deaths rose 44%, with the seven-day average ascending upward from 2,705 last week to 3,907 this week.

It’s unclear how much of a role Kraken is playing in the rise. Hospitalizations in the Northeast, where the variant has been dominant, were recently elevated, and New York hospitalizations were at their highest point in nearly a year. But they’re now on the decline. Experts told Fortune that other factors, like holiday gatherings, could be at play.

Still, the worry has been that hospitalizations could rise in other areas of the country, as Kraken begins flooding westward, as U.S. variants tend to do.

“The rise in hospitalizations being seen in the Northeast may eventually be seen throughout the U.S., if the XBB.1.5 subvariant is helping fuel this rise and this subvariant continues to spread throughout the rest of the country,” Dr. Bruce Y. Lee, professor of health policy and management at the City University of New York School of Public Health, recently told Fortune.

Dr. Michael Merson, visiting professor at New York University’s School of Global Public Health, told Fortune that Kraken's dominance is unsurprising, and that the country's increase in deaths "can be attributed, at least in part, to Kraken."

Deaths are a “lagging indicator” of COVID activity due to delays in reporting and are usually “reflective of what was going on in the prior two weeks,” Dr. Amesh Adalja, an infectious-disease specialist and senior scholar at the Johns Hopkins Center for Health Security, told Fortune.

Thus, the rise in deaths could simply be the result of a rise in cases, irrespective of variants.

“Most of the deaths that are occurring in the United States are in high risk people who are not boosted and not receiving Paxlovid,” he said. “This applies to any variant—not just the latest one making headlines.”

European CDC releases new Kraken risk assessment

A combination of two Omicron BA.2 strains, XBB.1.5 was projected to fuel 28% of U.S. COVID cases last week, according to the CDC. A Jan. 5 memo from the European Centre for Disease Prevention and Control (ECDC) had predicted U.S. dominance in short order. But the variant won't achieve European dominance this month, if at all, due to low levels of circulation, the ECDC said, adding that it may achieve dominance there in a month or two.

Kraken poses a low risk to the general population, and a moderate to high risk to vulnerable individuals like the elderly, immunocompromised, and unvaccinated, the ECDC said in a risk assessment of the new variant, released Friday.

There is currently no evidence that Kraken causes more severe disease than other Omicron variants, the agency said. A risk assessment released earlier this week by the World Health Organization came to the same conclusion, adding that the new variant also doesn't appear to be substantially more immune-evasive.

Kraken is estimated to double the number of people it sickens every nine days, and to have a 12% growth advantage in the U.S., according to the ECDC.

U.S. wastewater levels of COVID had been flirting with a No. 2 all-time high, potentially on track to surpass levels during this summer's BA.5 wave, which currently hold the title. Levels, however, were on a downward trend as of Wednesday, according to Biobot Analytics, a company that performs wastewater surveillance for the CDC.

This story was originally featured on Fortune.com

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