After the omicron variant sent coronavirus cases, hospitalizations and deaths soaring during winter months, the metrics are all on the decline in the US, prompting state and local officials to relax mitigation measures.
But a subvariant of omicron that is even more transmissible than the lineage that caused the worst coronavirus surge the US has ever seen is lurking, and experts warn it could prolong the latest wave as people are eager to drop their masks and move into a “new phase”Of the pandemic.
Cases of BA.2, one of four omicron subvariants, are roughly doubling each week. It was responsible for nearly 4% of new coronavirus cases last week, according to estimates from the Centers for Disease Control and Prevention. That’s up from 2% of cases the week before and 1% the week before that.
While the increase is small and slower than some predicted, experts warn that the relaxation of mitigation measures could help the subvariant take hold in the US
BA.2, which has been informally referred to as “stealth” omicron, is already the dominant lineage in 18 countries, according to the World Health Organization. It is considered even more infectious than other – already deemed highly contagious – omicron subvariants. Similar to the original omicron subvariant, it appears to decrease vaccine efficacy. It also shows signs of resistance to some monoclonal antibody treatments, according to preliminary research.
New findings out of Denmark that have not been peer reviewed also suggest BA.2 can reinfect people shortly after they recover from the more common lineage of omicron, though the occurrence is “rare” and is seen “mostly in young unvaccinated individuals with mild disease not resulting in hospitalization or death. ”
The start of BA.2’s spread in the US comes as every state but Hawaii has dropped or plans to drop indoor mask mandates.
The timing of ending mitigation measures presents challenges to understanding the subvariant, says Brianne Barker, an associate professor of biology at Drew University. For one, it makes it difficult to know how much of the BA.2 caseload increases are due to higher transmissibility versus opportunity since it started circulating as mitigation measures fell.
The removal of mask mandates while cases remain elevated could also give BA.2 a boost, according to Jennifer Surtees, an associate professor of biochemistry at the University of Buffalo.
Cartoons on the Coronavirus
“That’s where I worry about BA.2 potentially being able to get a foothold and finding people who do not already have immunity or have waning immunity,” Surtees says.
“If we stay the course a little bit longer, we could actually prevent BA.2 from getting a foothold,” she adds.
Both Barker and Surtees say BA.2 could prolong the omicron wave.
“When I look at this subvariant, it makes me think that the omicron wave… may be a little broader and may not come down quite as sharply as at the end of some of the others have,” Barker says.
But both are clear that the coronavirus is hard to predict, and things can change quickly. Still, Surtees says the subvariant probably won’t result in another dramatic increase in cases.
“I can see it sort of prolonging this current wave that we’ve got going on,” Surtees says. “But I think at this point, I’m not sure we’re going to see a second spike or peak the way we did when omicron came onto the scene.”
While the percentage of new coronavirus cases in the US from BA.2 is small, experts worry that it might not be an accurate estimate.
“It might be a little bit of a smaller increase that I might have imagined here, but I do not know if we are doing enough sequencing of enough cases to fully have confidence in that percentage,” Barker says.
Given how many people are relying on at-home COVID-19 tests, Surtees also has concerns about sequencing – or the analysis of coronavirus samples to determine the strain responsible for infection. Those tests do not get automatically reported to health departments and can not be sequenced. So even though more cases might be getting sequenced, it’s not an unbiased look at what is spreading across the country, according to Surtees.
And a decrease in coronavirus cases is leading to a decrease in coronavirus testing, which is worrying experts.
“We are very concerned about a reduction in testing around the world,” Maria Van Kerkhove, WHO’s technical lead on COVID-19, said on Tuesday, adding that some of the reported declines in coronavirus cases could be due to a lack of adequate testing .
Sequencing is also slightly more extensive for BA.2 compared to omicron’s other lineages. Previous omicron lineages generated a response from PCR tests that helped researchers quickly identify it. But BA.2 does not offer the same shortcut for sequencing, prompting the nickname “stealth” omicron. However, PCR tests still work on BA.2.
Is it BA.2? Is it “stealth” omicron? Should it get its own Greek letter?
The name of the subvariant has sparked a conversation about what the public should call BA.2.
“Stealth” omicron is an unofficial nickname for the subvariant. But some experts say that calling it by its official name – BA.2 – can be confusing for the general population and have suggested the subvariant get its own Greek letter apart from omicron.
A recent study out of Japan that has not yet been peer reviewed found that, in hamsters, BA.2 appeared to cause more severe disease than it’s more common counterpart, BA.1.
“It looks like we might be looking at a new Greek letter here,” Deborah Fuller, a virologist at the University of Washington School of Medicine, told CNN after reviewing the research.
Responding to increasing pressure, one of WHO’s advisory groups examined BA.2 to see if it was different enough from BA.1 to be distinguished by a new name. This week it announced that BA.2 would remain classified as omicron.
“Based on available data of transmission, severity, reinfection, diagnostics, therapeutics and impacts of vaccines, the group reinforced that the BA.2 sublineage should continue to be considered a variant of concern and that it should remain classified as Omicron,” WHO said in a statement on Tuesday.
WHO has acknowledged a genomic difference between BA.2 and other omicron subvariants but said that BA.2’s behavior in the real world is what is most important. And Van Kerkhove said that real-world data from several countries has not shown a difference in severity from BA.2 in terms of hospitalization rates.
“There are genetic differences but what we want to know is, is the virus behaving differently? Is BA.2 behaving differently than BA.1? ” she said. “It is more transmissible, yes. But in terms of severity, we are not seeing that – and that’s really critical. ”
Surtees says naming could depend on how the BA.2 situation plays out. If it starts making up more cases and prolonging the omicron wave, she says it could be useful for the public to have another Greek letter to limit confusion.
“There’s an argument to be made that it’s different enough at the genomic level that it could warrant its own Greek letter,” Surtees says. “However, at this point, I do not know that it is necessary.”
What seems to be certain, though, is that omicron will not be the last coronavirus variant.
“We can not predict exactly what will happen with the exception of knowing that more variants will emerge,” Van Kerkhove said.