New Subvariant 'Most Transmissible': What To Know About XBB.1.5 In IL

ILLINOIS — The new coronavirus subvariant XBB.1.5 — one global health officials call the “most transmissible” descendant yet of the omicron variant — could fuel new cases of COVID-19 in Illinois.

In the United States, XBB was responsible for more than 27 percent of cases last week, up from about 2 percent the first week of December, according to the Centers for Disease Control and Prevention.

In the Northeast, more than 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 of CDC COVID Data Tracker new infections.

In the Midwest region, the rate was about 7.5 percent with the majority of cases being reported in Minnesota, Michigan and Wisconsin, according to CDC data. In Illinois, about .13 percent of COVID cases are XBB for the week of Dec. 17, .12 the week of Dec. 24 and there were no cases reported of the strain the first week of 2023, according to data from the Illinois Department of Public Health.

“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.

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 Illinois, more than 2 million residents have gotten the new bivalent booster since it was authorized in the fall. Of Illinois’ total population, more than 78 percent have received at least one COVID-19 vaccine dose, 71 percent have completed their primary series of COVID-19 vaccines, and of the eligible population, more than 18 percent have received the bivalent booster dose, according to data from the Centers for Disease Control and Prevention.

“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.

In Illinois, the state reported The preliminary seven-day statewide total to be 128 COVID-19 cases per 100,000 residents. State health officials also reported that 1,766 individuals in Illinois were reported to be in the hospital with COVID-19. Of those, 233 patients were in the ICU and 77 patients with COVID-19 were on ventilators.

Jha said he’s concerned about XBB, but “Am I worried this represents some huge setback?” 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.