Are Omicron’s BA.4.6 or BA.2.75 subvariants threatening California?

As the latest wave of coronavirus fueled by Omicron’s super-infectious BA.5 subvariant continues to recede, health officials are wary of what may follow.

California experts are closely following two new sub-variants, BA.4.6 and BA.2.75, themselves members of the Omicron family. It is unclear whether they will eventually spread to worrying proportions in the state, but there is cause for caution as they have raised concerns elsewhere in the world.

The more pressing question is whether either can outperform BA.5, which essentially wiped out all other strains of coronavirus during its stunning surge this summer. If they can, it could potentially signal another spin in an all-too-familiar cycle, where the emergence of an even more infectious strain threatens to trigger a further rise in cases.

“The evolutionary pressure on the virus is to find a way around the immune wall that we’ve built,” White House COVID-19 response coordinator Dr. Ashish Jha said this week in a forum with the American Chamber of Commerce.

At this point, BA.5 is by far the most common version of the coronavirus circulating in California and across the country. It was estimated to constitute 88% of coronavirus cases nationwide for the week ending August 13, according to the US Centers for Disease Control and Prevention.

However, the proportion of infections attributed to BA.4.6 increased slightly. This subvariant was estimated at 5.6% of cases in the week ending August 13, compared to 5% the previous week.

More recent figures peg the respective estimated shares of cases of these subvariants at 89% and 6.3%, according to CDC data.

BA.4.6 is not a major player in the federally defined region which includes California, Arizona, Nevada, Hawaii and the Pacific Ocean territories. In this region, BA.4.6 accounted for about 2.2% of cases in the week ending August 13. However, it constituted about 14.2% of weekly cases in a central region of the country that includes Iowa, Kansas, Missouri and Nebraska. .

Meanwhile, the BA.2.75 sub-variant has attracted attention for becoming dominant in India and competing with BA.5 there, according to a Tweeter by Dr. Eric Topol, director of the Scripps Research Translational Institute in La Jolla.

“We are now seeing signs that it can compete with BA.4.6 in Australia as well,” Topol wrote. “Just the fact that variants can surpass BA.5 is of concern.

And a pre-print study by Chinese scientists suggested that BA.2.75 “could prevail” after the current wave of BA.5.

What this means for California and the United States is unclear.

There were many variants that ultimately failed. And, as Topol wrote, the trajectory of a variant like BA.2.75 “can vary significantly from country to country”.

In Los Angeles County, there is little information to suggest that either variant is experiencing dramatic growth. According to the most recent data, BA.4.6 accounts for just 1.5% of cases in LA County, a rate that remains relatively the same from the previous week.

There were only three BA.2.75 specimens identified cumulatively over a six-week period, “indicating no increased circulation of this sublineage in LA County,” said the Director of Public Health, Barbara Ferrer.

“At this time, as you can see, there are no sub-variants or sub-lines that are poised to circulate more widely in LA County than BA.5,” Ferrer said. “This is good news, as our recent history has linked a proliferation of new strains to increased transmissibility.”

But reports from elsewhere of subvariants outperforming BA.5 are concerning, Ferrer said.

“I don’t know if there’s a connection to the environment, the weather, or any particular conditions, including the vaccination status of residents of these communities, as well as previous infections people have had,” he said. she declared. “It’s hard for us to really sort everything out from California here. I know we have to watch it carefully.

For now, however, LA County and California as a whole continue to experience a pandemic reprieve — with a sustained decline in both newly reported infections and the number of coronavirus-positive hospital patients.

“Given the significant decline in cases over the past two weeks and the absence of increased circulation of a new strain of the virus, we are optimistic that hospitalizations will also continue to decline in LA County over the next few months. next two to three weeks,” Ferrer said.

Los Angeles Times

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