Rebounding?

Coronavirus cases are rising again in L.A., San Diego and San Francisco

Amaya Palestino, 6, gets immunized against COVID-19 on March 16 at Helen Keller Elementary School in Lynwood. (Luis Sinco / Los Angeles Times)

Coronavirus cases have begun to rise in Los Angeles, San Diego and San Francisco counties, likely a result of the highly contagious Omicron subvariant BA.2, decreased use of masks and waning

immunity.

The increases are modest, and it's unclear whether this is a brief hiccup, the beginning of a larger wave of cases or something in between.

"I think that it's possible we might see a modest uptick in the next few weeks due to the fact that we are reducing some of the restrictions, such as indoor mask use," UCLA epidemiologist Dr. Robert Kim-Farley said. "But I do not anticipate that we would see a major surge at this stage, just because so many people are immune, due to natural infection or vaccination."

L.A. County has also observed an uptick in coronavirus outbreaks at K-12 schools: There were 10 last week — the most in a single week since mid-February — versus four the previous week.

The trends in some of California's most populous areas echo what has been seen in parts of the East Coast, where a small wave has begun in New York and Massachusetts. BA.2 — which became dominant faster in the Northeast than on the West Coast — now comprises an estimated 72% of new weekly cases in the U.S., up from 57% the previous week.

While BA.2 accounts for 75% of cases in New England, New York and New Jersey, it accounts for 61% along the West Coast. Globally, 86% of new coronavirus cases over the past month were due to BA.2, according to the World Health Organization.

BA.2 is considered to be 30% to 60% more contagious than the earlier Omicron subvariant, BA.1.

In Western Europe, the new subvariant has had varied effects.

Britain endured a significant second Omicron wave that placed pressure on hospitals and caused the death rate to rise. The surge, fueled by BA.2, has brought weekly coronavirus cases to about 40% of the level from the first Omicron surge. Case rates now appear to be declining, UC San Francisco epidemiologist Dr. George Rutherford said at a campus meeting last week.