XBB.1.5 Coronavirus Subvariant: What Wisconsin Residents Should Know

WISCONSIN — As the coronavirus subvariant XBB.1.5 becomes more prevalent in much of the country, Wisconsin could soon see the same. Some global health officials call it the “most transmissible” descendant yet of the omicron variant.

Across the United States, XBB was responsible for over 27 percent of cases last week, up from about 2 percent in the first week of December, according to the Centers for Disease Control and Prevention. The strain appears to be especially prominent in the Northeast states, where over 70 percent of cases are believed to be XBB, according to the CDC COVID-19 tracker. In other regions, the strain is estimated at less than a third new infections.

“That’s a stunning increase,” White House COVID-19 response coordinator Dr. Ashish K. Jha tweeted last week of the rapid rise in XBB cases, at the same time telling Americans it’s “critical” that Americans are up-to-date on bivalent booster shots.

Closer to home, the variant seems to not be as prevalent, but it's being detected.

In the region including Wisconsin, Illinois, Indiana, Minnesota and Ohio, about 7.3 percent of cases are XBB.1.5 in the past week, according to CDC data. The University of Wisconsin - Madison State Laboratory of Hygeine also tracks the different variants of the coronavirus.

For the week starting Dec. 12, the state hygiene lab detected one case of XBB 1.5, accounting for less than 1 percent of the samples sequenced. The next week the lab conducted fewer sequences, but XBB 1.5 accounted for 9 percent of the total detected.

Only about 15 percent of eligible Americans have gotten their bivalent booster shots. That includes 38 percent of older Americans, who are most at risk of a serious illness.

In Wisconsin, 21 percent of people older than five have received their updated booster vaccination.

“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,” Jha tweeted.

XBB.1.5 combines traits of previous mutations, which health experts say make it spread more easily, even among previously infected or vaccinated people.

It’s more transmissible because of the mutations it has that allow the “virus to adhere to the cell and replicate easily,” Dr. Maria Van Kerkhove, technical lead on COVID-19 for the World Health Organization, told reporters last week.

“The more this virus circulates, the more opportunities it will have to change,”

There is no evidence XBB is more severe than other omicron strains, Van Kerkhove said.

“We are concerned about its growth advantage, in particular in some countries,” Van Kerkhove said, singling out Europe and the Northeast U.S., “where XBB.1.5 has rapidly replaced other circulating variants.”

COVID-19 infections have declined over the past year, to 470,699 weekly cases on Jan. 4, down from last year’s high of more than 5.6 million cases a week on Jan. 19, 2022.

Wisconsin also saw its peak caseload in January of 2022, with over 160,000 cases. This past week, the state reported just over 6,500 cases, according to data from the CDC.

Jha said he’s concerned about XBB, but “Am I worried this represents some huge set back?” he said. “No.”

Besides getting a bivalent vaccine, Jha said Americans should take COVID-19 tests before large gatherings or if they will be seeing someone who is vulnerable. Also, he said, wear high-quality facemasks in crowded indoor spaces, and “work to improve ventilation/filtration in indoor spaces.”

Anyone showing symptoms should get tested right away. The Paxlovid Molnupiravir treatments “should work fine based on what we know,” he said.