The new and highly contagious COVID variant dubbed XBB.1.5 roughly doubled its prevalence in the Midwest over the last week and experts say that growth will likely continue in the weeks ahead.
The variant now makes up 43% of cases in the U.S. and more than 14% of cases in the Midwest, climbing in both metrics from 30.4% and roughly 7% the week prior, according to estimates from the Centers for Disease Control and Prevention.
The growth isn't unexpected as the omicron subvariant has been described as one of the most contagious variants of the pandemic so far.
Experts in the Chicago area have been preparing for the variant to surge in the Midwest after the Northeast saw a rapid rise, with the variant now making up more than 80% of cases there.
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"I do expect that [XBB.1.5] will continue to increase here," Chicago Department of Public Health Commissioner Dr. Allison Arwady said Tuesday.
Arwady said the area isn't expecting to see a surge in COVID cases or hospitalizations that mirror the start of the omicron variant or the height of the pandemic, but did say there is potential for a mask advisory if cases rise along with the variant. Such an advisory has not yet been issued, with much of the Chicago area remaining at a "medium" community level, per the CDC.
Unofficially dubbed the "kraken" variant, the highly contagious "recombinant" variant is composed of two different BA.2 strains.
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"We definitely expect that this virus, this variant will continue to increase in proportion," Hannah Barbian, a virologist who tracks COVID variants with Rush University Medical Center, told NBC Chicago as cases of the new subvariant have already been detected in the city. "So likely what we've seen in the East Coast, will happen in Chicago as well."
Dr. Ashish Jha, White House COVID czar, tweeted last week that the variant is likely more immune evasive, even "more than other omicron variants."
Maria Van Kerkhove, the WHO’s COVID-19 technical lead, described it as the most transmissible version of COVID yet.
Experts believe a mutation allowing the variant to bind better to cells is behind its ability to spread so quickly.
"The virus needs to bind tightly to cells to be more efficient at getting in and that could help the virus be a little bit more efficient at infecting people," Andrew Pekosz, a virologist at Johns Hopkins University, told CNBC.
Jha echoed that finding, saying the variant "binds more tightly to the human ACE receptor," which can affect contagiousness.
While it's not clear where the variant originated exactly, Arwady said it has so far not shown signs of leading to more severe infections.
While there are significant concerns surrounding the new strain, it remains an omicron subvariant, Arwady added, which offers less risk than if the variant were in an entirely different family.
Experts have said the bivalent COVID booster appears to offer some protection against the newer strains, particularly against severe illness, in large part because they remain under the omicron family.
"It does look like the vaccine, the bivalent booster is providing continued protection against hospitalization with these variants," Pekosz told CNBC. "It really emphasizes the need to get a booster particularly into vulnerable populations to provide continued protection from severe disease with these new variants."
But Jha noted that for those who had infections before July or who haven't received a bivalent COVID booster shot, protection is much lower.
"Right now, for folks without a very recent infection or a bivalent vaccine, you likely have very little protection against infection," he tweeted.
Arwady previously noted symptoms haven't changed with the new variant, though she said symptoms similar to the flu are less common, particularly in those who are vaccinated and boosted.
"COVID is showing up very much like it already has. I think, if anything, we are seeing it a little bit less likely to have the more severe symptoms," Arwady said last week. "Definitely people get the severe symptoms still, especially if they're not up-to-date with their vaccines. But more often now we are seeing people - especially if they're fully up-to-date, maybe it's their second time getting COVID, whatever it might be - we're seeing more people actually just have cold-like symptoms, less likely to have those flu-like, really feeling very sick, the high fevers."0
