A reflection of a runner looking at the Cal student store in Berkeley, Calif., on July 21, 2021. (Harika Maddala/ Bay City News)

Alameda County health officials announced Thursday that they are reinstating the county’s indoor mask mandate as COVID-19 cases and hospitalizations continue to increase locally and across the Bay Area.

The mandate will go into effect at 12:01 a.m. Friday and will apply to most indoor public settings, including grocery stores and gyms.

Students and staff at K-12 schools will not be required to wear masks under the order through the end of the 2021-2022 school year, according to the Alameda County Health Care Services Agency, but they will be required in all other settings for children including summer school and youth programs.

The order will not apply to the city of Berkeley, which operates as its own local health jurisdiction. A spokesperson for the city did not respond when asked whether Berkeley will align with the county.

“Rising COVID cases in Alameda County are now leading to more people being hospitalized and today’s action reflects the seriousness of the moment,” county Health Officer Dr. Nicholas Moss said in a statement. “We cannot ignore the data, and we can’t predict when this wave may end.”

Alameda County is the first county in the Bay Area to reinstate mask requirements in indoor public settings since February, when the state and most counties in the greater Bay Area lifted mask requirements that were implemented to combat the winter surge driven by the omicron variant.

Santa Clara County was the lone holdout among the 11 counties in the greater Bay Area, keeping its indoor mask requirement in place until March 2.

Health officials have urged a return to widespread masking in recent weeks amid a new surge in cases primarily spurred by the omicron subvariant BA.2.

According to Alameda County health officials, COVID cases began to rise in April and the daily number of reported cases has eclipsed the peak of last summer’s wave driven by the delta variant.

Local COVID hospitalizations have also risen to 102, as of Monday, after falling as low as 37 in early April.

COVID cases in general are largely undercounted, according to health officials, due to the wider availability of at-home tests that do not necessarily get reported to the county and infections that may remain asymptomatic and undetected.

“Putting our masks back on gives us the best opportunity to limit the impact of a prolonged wave on our communities,” Moss said.

COVID information and resources for Alameda County can be found at https://covid-19.acgov.org/index.page.