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Another strain of COVID-19 is sweeping the Northeast and is increasing already in Michigan. But much remains unknown about XBB.1.5. (Bridge photo by Dale Young)

A new subvariant of COVID-19 — called the “most transmissible” variant yet — could sweep Michigan within weeks after emerging as the dominant variant in the Northeast.

This story also appeared in Bridge Michigan

Named XBB.1.5, it’s the latest subvariant of omicron, which first slammed Michigan in December 2021 and resulted in the highest infection rates of the pandemic.

In just four weeks XBB.1.5 has gone from a third of all cases in the Northeast — Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island and Vermont — to now 73 percent.

And it composes a third of all cases in the Mid-Atlantic region, up from 9 percent four weeks ago. Nationwide, it was 27.6 percent of all cases last week.

So far, it’s a relatively minor presence in the Midwest, representing just under 8 percent of all cases.

Still, its share of cases in the region composed of Michigan, Illinois, Ohio, Indiana, Wisconsin and Minnesota has risen from 1.6 percent four weeks ago, according to the Centers for Disease Control and Prevention.

Hospitalizations are up slightly in the Northeast states of Connecticut, Massachusetts, Maine and Rhode Island but have fallen markedly in Vermont and New Hampshire.

Little is known about XBB.1.5, which a World Health Organization official called the “most transmissible” last week. 

Dr. Ashish K. Jha, the White House’s COVID-19 response coordinator, said on Twitter that he is concerned because XBB.1.5 is more likely to evade immunity than other strains of COVID-19. 

“Am I worried this represents some huge set back? No,” he wrote.

“We will soon have more data on how well vaccines neutralize XBB.1.5,” he wrote on Twitter. “But right now, for folks without a very recent infection or a bivalent vaccine, you likely have very little protection against infection. And for older folks, diminishing protection against serious illness”

Researchers and health officials, though wary of a potential surge in new infections, do not know yet whether XBB.1.5 will cause more severe illness,  but early indications are it does not, according to Food and Drug Administration Commissioner Robert Califf.

The variant has been detected in small numbers in Michigan, said Lynn Sutfin, a spokesperson for the Michigan Department of Health and Human Services. 

“Early indications are that the bivalent vaccine offers protection against severe illness and remains our best defense against COVID-19,” she said in an email to Bridge Michigan.

Dr. Matthew Sims, director of infectious disease research for Corewell Health East in Royal Oak, said it appears that Paxlovid, the antiviral pill designed to minimize illness after an infection, continues to work on those infected with XBB.1.5.

In Michigan, the number of COVID-19-positve hospital patients has plateaued recently after a rise that started in December. 

As of Monday, there were 1,267 COVID-19 patients being treated, down from 1,361 on Friday and 1,416 last Wednesday, which was the highest level since February.

Sims said that many COVID-19 patients in his hospitals, which were formerly part of the Beaumont Health system, are being treated for other ailments, not COVID-19.

When omicron first hit Michigan, hospitals were treating as many as 5,000 COVID-19-positive people in January 2022.

Sims continues to advocate that people hoping to avoid COVID-19 wear masks in crowded public spaces and stay up-to-date with the coronavirus vaccines, which remain effective, he said, at reducing the severity of illness if someone contracts COVID-19.

The number of new weekly confirmed coronavirus infections in Michigan has declined for the past three weeks, with the state reporting 7,930 confirmed infections last week, down from 8,703 the previous week and 11,074 the week ending Dec. 20.

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