COLUMBUS, Ohio — The BA.2 sublineage of the COVID-19 omicron variant is gaining ground on the original omicron strain, though health experts are split on what it means for the virus outlook this spring.
What You Need To Know
- The BA.2 sublineage represents more than half of the most recent sequenced cases globally
- In the U.S., the CDC says that the BA.2 sublineage accounts for 11.6% of new cases
- Health experts are unsure if virus cases will rise because of the BA.2 sublineage
This week, a World Health Organization advisory group issued a statement that said BA.2 “has been increasing relative to BA.1 in recent weeks, and is the predominant omicron lineage in several countries,” while the Centers for Disease Control and Prevention updated data to say that BA.2 represents 11.6% of U.S. cases.
In the last three weeks, the BA.2 lineage has represented 52% of omicron cases submitted to the global research database. In the U.S., BA.2 represents about 8.4% of sequences in that timeframe, according to the database.
BA.1 and BA.2 have common mutations, but the lineages have numerous separate mutations, explained Mark Zeller, a staff scientist in a Scripps Research lab that tracks variant trends at the site outbreak.info.
Researchers are performing genomic sequencing of positive COVID-19 samples to determine the proportionality of variants, but it’s actually possible to differentiate between BA.1 and BA.2 with certain PCR tests. The PCR data provides a more in-the-moment picture of the variant landscape, because genomic sequencing results are often not available for 2-3 weeks.
Based on recent analysis of PCR testing in San Diego and at another lab in southern Connecticut that's tracking the sub-lineages with PCR testing, BA.2 is likely already dominant in those populations, Zeller said. Genetic sequencing will likely confirm this soon, he said.
“In a week from now, we will see this exact same thing in the sequence data, but we can already see it happening right now. It grows quite fast, and that’s also because the case numbers are low or fairly low compared to early January, for example, so it's easy, sort of, to take over,” Zeller said. “It's not going to be as lightning fast as the first omicron because that was absolutely insane.”
Zeller said he thinks BA.2 shouldn’t be classified as a subset of omicron — he said it should get its own Greek letter.
“It's like a 20 nucleotide change, which is the difference between alpha and delta,” Zeller said. “And a lot of these differences are also in the spike gene actually."
While BA.2 doesn't appear to be more virulent, Zeller said he believes it will cause a small surge in COVID-19 cases.
"I think there will just be another surge like in the next weeks, months, but I mean, I don't think it's going to be a big one. Cases will go up slightly, but it won’t be as bad as in January," he said. "Not even close."
Ohio State University has detected 35 cases of BA.2, with the first detection in a Jan. 7 sample, according to submissions to the global research database.
Sara Koenig, director of COVID-19 advanced technologies at the Ohio State College of Medicine, said the university's labs have not seen any rapid growth in BA.2 yet from their surveillance of cases in central Ohio.
“We have been seeing very low prevalence of BA.2,” Koenig said in an interview. “We have seen BA.2 since January, but we don't see an increasing trend at this point. It has been circulating between 0 to 4%, depending on the week.”
Koenig thinks it’s likely BA.2 will out compete BA.1, but she said the process may not be sudden like when omicron surpassed delta. If BA.2 does become dominant, she's not sure that cases would surge.
“India is a great example, where they were approximately 90% BA.1 in January and then BA.2 really took over India,” Koenig said. “They have a really nice recovery from their peak, so they're basically down to baseline now if you look at their current numbers."
WHO said in its statement there is some good news about the BA.2 sub-lineage, based on early information.
“Reinfection with BA.2 following infection with BA.1 has been documented, however, initial data from population-level studies suggest that infection with BA.1 provides substantial protection against reinfection with BA.2, at least for the limited period for which data are available,” the WHO statement said.
Ohio Health Director Dr. Bruce Vanderhoff said he is not particularly concerned about the BA.2 sub-lineage. He said in the state’s most recent data, more than 90% of the recent omicron sequences have been BA.1, with BA.2 accounting for the remainder of Ohio's cases. COVID-19 cases that aren’t omicron are rare, he said.
“We see both BA.1 and BA.2 here in Ohio — by far mostly BA.1 — and we're not seeing a change in the BA.2 to BA.1 proportion, nor would I expect that we're going to see much of a shift there,” he told Spectrum News during a news conference Thursday. “They’re really two sub-variants within a family.”
Previously, WHO has said that BA.2 is more transmissible than BA.1, but it noted that the difference in transmissibility is “much smaller” than the difference between delta and omicron. The organization said BA.2 should be classified as a sub-lineage, not as a new variant of concern. WHO also reported cases have been declining globally as BA.2 has risen in prevalence.
U.S. COVID-19 hospitalizations have fallen from more than 150,000 at the peak of the omicron wave down to just above 32,000 as of the latest update.
As of the CDC’s latest update Thursday, more than 98% of Americans are in a location with “low” or “medium” community levels, which means the agency does not recommend required masking.
Koenig said sequencing will continue to be a priority at Ohio State and at other labs during the current lull in cases.
"As we move into the endemic phase, sequencing is going to be critical so that we can monitor new variants," Koenig said. "We expect the virus to continue to mutate, and so having an eye on what it looks like at all times is really going to help us create the best policies and come up with additional vaccines."