The omicron subvariant BA.5 is beginning to lose its grip on the U.S., making room for other strains to compete for dominance.
At one point in August, the highly transmissible variant made up over 99% of new coronavirus infections. But now, BA.5 only accounts for about 67% of new cases, according to the Centers for Disease Control and Prevention.
Health experts say it's difficult to accurately capture how prevalent these new variants are as most Americans test at home and fewer samples are available for genetic sequencing. Even so, it's clear there are a handful of strains pulling ahead.
"They're doing what viruses do," said Andrew Pekosz, a virologist and professor at Johns Hopkins Bloomberg School of Public Health. The "parent BA.5 seems to be dropping off in numbers but what's taking its place is second and third generations of it."
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BA.4.6
Parental strain: BA.4
Prevalence: An estimated 12.2% of new cases this week
What to know: The share of BA.4.6 infections has been increasing for "several months," said William Hanage, an infectious disease epidemiologist at the Harvard T.H. Chan School of Public Health.
Mutations: The strain is a descendent of the BA.4 omicron subvariant, but contains a couple of key mutations to the spike protein that health experts speculate may give it an advantage. One such mutation, R346T, has been seen in previous variants and is thought to be associated with immune evasion. Initial data suggests BA.4.6 has been able to evade immunity, "but not to a high extent," Pekosz said.
BQ.1 and BQ.1.1
Parental strain: BA.5
Prevalence: Combined, an estimated 11.4% of new cases this week
What to know: BQ.1 and BQ.1.1, the newest strains, have gained the attention of top health experts due to its rate of increase since it was first identified in early September. “This has a pretty troublesome doubling time,” President Biden’s chief medical adviser, Dr. Anthony Fauci, said in an interview with CBS News.
Dr. Peter Hotez, a pediatrician and dean of the National School of Tropical Medicine at Baylor College of Medicine Houston, called BQ.1.1 on Twitter the “most likely candidate” to drive a new COVID-19 wave, if that were to happen in the coming months.
Mutation: The strains also contain the R346T mutation that has been linked to immune evasion.
BF.7
Parental strain: BA.5
Prevalence: An estimated 5.3% of new cases this week
What to know: "It is also picked up a few mutations we know will evade vaccine induced immunity so we’re keeping an eye on it to see how much of that immunity it will evade," Pekosz said.
Mutation: BF.7 is another descendent of BA.5 with the R346T mutation.
The good news
Although most of the emerging variants contain a mutation that may be able to evade vaccine-induced and natural immunity, health experts say the new bivalent booster should provide some protection against the newest strains. The boosters combine the original COVID-19 vaccine with a reformulation that targets the BA.4 and BA.5 versions of the omicron variant.
"These (variants) are related to the BA.5 that is in the bivalent vaccine," Pekosz said. "Much of the immune response that you'll get from the vaccine will continue to recognize these new BA.4 and BA.5 variants."
For now, health experts don't foresee any of the new variants causing a surge akin to that of omicron in early 2022. But they urge Americans to get boosted to prevent severe disease and reduce transmission.
As of Oct. 12, the CDC reports about about 14.8 million Americans have gotten their updated booster.
"If people went out and got the vaccine, they'd be able to boost their protection against these variants and limit spread of these viruses before they evolve more mutations," Pekosz said.
Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT.
Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.
This article originally appeared on USA TODAY: New COVID variants are emerging: BA.4.6, BQ.1, BQ.1.1 & BF.7 explained
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