The subvariant of omicron known as BA.2 accounts for about one-fourth of COVID-19 cases sequenced in Washington, according to the state’s largest genomic sequencing lab.

The subvariant has steadily spread in the state, and across the country and Europe, but researchers are hopeful any potential wave of the new strain won’t cause as many infections, hospitalizations and deaths as the original version of the variant did.

The new subvariant, which emerged in the United Kingdom in December, was identified in Washington in January and has remained at fairly low levels since then, state epidemiologist Dr. Scott Lindquist said last week. Now early data from the state Department of Health and the UW Medicine clinical virology lab show the proportion of cases involving the variant has increased over the past month or so.

“It’s been sort of slowly creeping up over the last six weeks,” Alex Greninger, assistant director of UW Medicine’s virology lab and an assistant professor of lab medicine and pathology, said in a Tuesday statement. “It’s going to be interesting to see what the end of April, beginning of May, what that time period will look like.”

While virologists don’t yet have a clear timeline for a potential rise in cases, Greninger encouraged residents to pay attention to their local COVID trends and assured people that vaccinations — particularly booster shots — will continue to protect against severe infection.

“There’s great data that shows a BA.1 infection does protect against BA.2,” he said, referring to the different subvariants of omicron. “They’re very similar in that world from an immunological standpoint.”


In Washington, BA.2 accounted for about 3.7% of the coronavirus variants sequenced in the first week of February, according to a recent DOH variant report. By the end of the month, the subvariant made up about 9.4%.

Globally, the subvariant could already be slowing in some countries.

The Institute of Health Metrics and Evaluation — a research center at the University of Washington that’s been tracking COVID trends since the beginning of the pandemic — estimates the U.K. saw more than 270,000 daily infections last week, which also includes people who haven’t been tested. As of Tuesday, estimated infections were about 260,000, according to the institute’s data.

The center also projects a steady decline in U.K. cases through April and May.

Neither the United States nor Washington, meanwhile, have recorded a significant increase in COVID infections due to the subvariant. Data for the state, however, usually lags by at least a week.

King County, which provides more recent data, reported an average of 163 daily infections, a 15% decrease in cases in the past week, on Tuesday. During the recent surge of omicron cases, the county peaked at an average of 6,642 daily infections in January.

“Yes, we’ve detected [the current variant] for a month-plus now but it has not had the rapid increase like the initial omicron variant,” Lindquist said last week.