SEATTLE — A subvariant of the omicron COVID-19 strain, BA.2, now accounts for 25% of new COVID-19 cases sequenced by UW Medicine, according to a release from the school.
The subvariant has been linked to the spread of COVID-19 cases in Europe and Asia and has been spreading gradually in the United States. UW Medicine first identified a case of the subvariant in January.
“It's been sort of slowly creeping up over the last six weeks,” said Dr. Alex Greninger, the virology lab’s assistant director and an assistant professor of lab medicine and pathology at the UW School of Medicine in Seattle.
Greninger said he is hopeful a potential wave of cases caused by BA.2 wouldn’t be worse than the wave caused by the original omicron variant. The school cited data showing people who were infected by the original omicron variant are likely protected against BA.2.
“It’s going to be interesting to see what the end of April, beginning of May, what that time period will look like,” said Greninger.
BA.2 now accounts for about 35% of new COVID-19 cases in the United States, according to data from the Center for Disease Control (CDC). At the present time, the majority of cases are still linked to the original omicron variant.
Washington state’s seven-day rolling average of COVID-19 cases is still on a decline, according to data from the Department of Health. The state’s current average is 498 cases over a seven-day period, down from the rolling average of 19,228 cases over a seven-day period at the peak of the omicron outbreak in January.
Dr. Ali Mokdad with the Institute of Health Metrics and Evaluation (IHME) said the state is not projected to have a surge in new COVID-19 cases in the coming weeks, although outbreaks are occurring in some places in Europe.
“Our models suggest that after the end of March, there should be a steady further decline in transmission,” Mokdad tweeted on Tuesday.
Surges in Europe appear to be related to changes in mask-wearing and social distancing behavior, Mokdad said. The Netherlands' most recent surge of BA.2 cases appears to have already peaked.
Mokdad said a fourth dose of the COVID-19 vaccine to target the BA.2 variant is not warranted for most people, aside from those of advanced age or people with co-morbidities.
“Even if transmission does increase for a period due to reduced mask use and social distancing combined with BA2, we do not think that implementation of mask and social distancing mandates would be warranted,” Mokdad wrote.