Here Are Omicron Ba.4.6 and Ba.2.75. Should California Be Worried?

Health experts are keeping a careful eye on the future as the latest coronavirus wave fuelled by the super-infectious Omicron subvariant BA.5 begins to wane.

Two newer subvariants, BA.4.6 and BA.2.75, both of the Omicron family, are being actively monitored by specialists in California. There’s reason to pay watch because they’ve generated alarm in other parts of the world, but it’s unclear if they’ll expand to worrying levels in the state.

The biggest concern is whether or not either can compete with BA.5, which has suddenly risen to dominance among coronavirus strains this summer. If they do, it may be a sign of a new round in an all-too-familiar cycle, in which the appearance of a more lethal strain of the virus threatens to cause a surge in new infections.

Dr. Ashish Jha, the White House’s COVID-19 response coordinator, stated last week in a discussion with the U.S. Chamber of Commerce that the virus is under “evolutionary pressure” to find a means to circumvent the immunity wall that has been constructed.


At now, BA.5 is by far the most widespread coronavirus strain in California and the United States. According to data from the U.S. Centers for Disease Control and Prevention, it was responsible for an estimated 89% of all coronavirus cases in the country for the week ending on Saturday.

However, BA.4.6 now accounts for a slightly higher percentage of all infections. Over the week ending on Saturday, this subvariant was expected to account for 6.3% of instances, up from 5.6% the previous week.

In the federally recognized territory that encompasses the states of California, Arizona, Nevada, Hawaii, and the Pacific Ocean territories, BA.4.6 does not play a significant role. An estimated 2.4% of cases in that area were caused by BA.4.6 last week, and most of those occurred during the week ending on Saturday. Still, in the Midwest (Iowa, Kansas, Missouri, and Nebraska), it accounted for around 16% of weekly cases.

On the other hand, a tweet from Dr. Eric Topol, head of the Scripps Research Translational Institute in La Jolla, has brought attention to the BA.2.75 variety because it has become prominent in India and is competing with BA.5 there.

There are “now indicators it can also compete with BA.4.6 in Australia,” Topol stated. “The fact that variations may compete with BA.5 is worrying in and of itself.”

In addition, a Chinese preprint study concluded that BA.2.75 “may triumph” after the current BA.5 wave.

It is unclear what this development signifies for California and the United States.

Many iterations have come and gone without gaining any traction. Topol also noted that the spread of a variety such as BA.2.75 “may vary greatly” from one country to another.

There is scant evidence that either of these subtypes is rapidly expanding in Los Angeles County. The most current numbers show that BA.4.6 accounts for only 1.5% of cases in L.A. County, a percentage that is essentially unchanged from the week before.

Public Health Director Barbara Ferrer noted that in the past six weeks, just three BA.2.75 specimens had been found, “showing no increasing circulation of this sublineage in L.A. County.”

As can be shown, no other subvariants or sublineages are currently more likely to spread widely in L.A. County than BA.5, as stated by Ferrer. This is encouraging because novel strains have been associated with higher rates of transmission in previous years.

Ferrer expressed concern over rumors of BA.5’s subvariants gaining market share.

When asked about possible causes, she stated, “I don’t know if there’s some relationship to the environment, the weather, or certain conditions, including the vaccination status of the population in those communities, as well as earlier diseases that folks have encountered.” Here in California, it’s difficult to tease it all out. We need to keep a close eye on it, that much I know.

But for the time being, both Los Angeles County and the state of California are enjoying a pandemic reprieve, with declining numbers of newly reported illnesses and hospitalized coronavirus-positive individuals.

We are optimistic that hospitalizations in L.A. County will continue to fall as well over the next two to three weeks, given the dramatic decline in cases these past two weeks and the absence of increasing circulation of a new strain of the virus, added Ferrer.

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