New evolution of the coronavirus's omicron variant could mean the virus is becoming more "steady" and "flu-like," said Trevor Bedford, a leading infectious disease scientist in Seattle who has tracked the virus's genome since the pandemic began.
Local and global researchers are attempting to predict how the virus might evolve over the next year as new COVID-19 resources roll out, including the federal government's new pandemic early warning system launched on Tuesday.
One theory comes from a team led by Bedford, who studies the coronavirus and its evolution at the Fred Hutchinson Cancer Research Center.
The idea that the coronavirus will one day look similar to seasonal influenza has been widely discussed over the past year, though last winter's emergence of omicron and its unusually rapid spread prompted a lot of questions about the theory. Now, more research about how omicron's subvariants have evolved has shed new light on the topic, Bedford said during a Tuesday webinar hosted by UW Medicine and Fred Hutch.
Since January, three omicron lineages have emerged — BA.1, BA.2 and BA.3 — with each differing in how they spread through communities, he noted. BA.2's advantage over BA.1, for example, appears to be that BA.2 is more transmissible, while omicron's spread last December was most likely due to waning population immunity.
Because BA.2 has become the dominant strain in the United States — including in Washington state — researchers expect further sublineages to stem from that subvariant, he said.
According to Bedford, the "one to watch," based on the number of mutations, is a sublineage spreading in New York and Massachusetts called BA.2.12.2. One noticeable mutation that appears in BA.2.12.2, Bedford said, is a mutation on the same spike that "appeared to have an important role in promoting the spread of (the delta variant)."
Lineages BA.4 and BA.5 have also been spreading in South Africa, and share a spike mutation with BA.1 and BA.2.
"All three of these then have about the same apparent advantage as BA.2 did over BA.1, so we'd expect a growth over the coming months, rather than these immediate, large epidemics," Bedford said Tuesday.
He added on Twitter that he generally expects future evolution to occur in a gradual accumulation of mutations in the coming months, similar to influenza viruses — rather than how omicron likely came about, which Bedford and other researchers think happened when the virus incubated in an immunocompromised person with a chronic infection for a year or more.
Some predictions aren't yet clear, however, and Bedford added that more recent, targeted experiments are needed.
In Washington, BA.2 continues to make up the largest proportion of circulating variants. The initial omicron strain accounts for 38.1% of variants, while BA.2 makes up about 61.9%, according to the state Department of Health's weekly sequencing and variants report.
Cases are still gradually ticking up in Seattle and King County, which this week is reporting an average of about 550 daily infections. Infection rates are highest in South King County, including in Auburn, Kent and Federal Way — which last week reported a 56% increase in cases — while Bellevue, Issaquah and Mercer Island recently saw a 16% decrease in cases.
