As the latest COVID surge persists, with hospitalizations and cases seemingly not yet a crest in Alameda County, county Health Officer Dr. Nicholas Moss has reinstated a broad mask mandate that we haven't seen the likes of for several months.

"We cannot ignore the data, and we can’t predict when this wave may end," Moss said in a release Thursday. "Putting our masks back on gives us the best opportunity to limit the impact of a prolonged wave on our communities."

The announcement did not specify what types of indoor settings should broadly be enforcing mask-wearing again, only that K-12 schools that are still in session can continue maskless through the end of the school year. Also, the city of Berkeley can set its own rules as it has its own public health department — and Berkeley did the opposite of the county two weeks ago, mandating masks in schools but not elsewhere.

Alameda County, like the rest of the Bay Area, aligned with the state back in February in lifting its mask mandate, and most public transit systems besides BART have lifted theirs as well.

The current surge in COVID cases, attributed primarily to the Omicron subvariant BA2.12.1 but potentially also being pushed by other subvariants that have been detected in wastewater, has caused widespread infection in the Bay Area in the last six weeks, particularly among those not previously infected or those infected with early strains of COVID. Earlier this week, based on data from the previous week, UCSF's Dr. Bob Wachter warned that this was a "big-time" surge in San Francisco and the chances of transmission in indoor public spaces was again very high.

Since then, the seven-day rolling average of cases has dropped slightly, however it may rise again with data coming in from Memorial Day Weekend and after. With the city reporting around 500 new daily cases in the official count, Wachter estimates that equates to about 2,000 actual cases, with 3 out of 4 likely going unrecorded.

UCSF infectious disease specialist Dr. Monica Gandhi said last week that she believed this surge would crest in early June, and be on the quick downslide by late June. But such predictions have not always proven true.

In related news, Ghandi pointed to a new study out Wednesday in Nature Microbiology suggesting that the T-cell response in the body from the existing vaccines is similar across all COVID variants so far, from Alpha to Omicron, which is what we have to thank for the drop in deaths and severe disease overall.

The move by Alameda County appears likely to be a lone one in the region, as previous mandates have been undertaken in concert by a coalition of county health officers. The Chronicle heard from health departments in Contra Costa, San Mateo, Napa, Sonoma and Solano counties that no new mandates are in store, but SF, Marin, and Santa Clara counties did not confirm.

In San Francisco, hospitalizations have been nearly flat since May 20, and dropped slightly on Wednesday from 106 to 99. The number of those hospitalized in Alameda County with COVID rose from 129 on May 20 to 155 on Wednesday, a 20% jump in two weeks.

Related: Dr. Monica Gandhi: Models Suggest Current COVID Surge Will Be Over By Pride Weekend

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