Add most of the Bay Area to the growing list of California counties urging residents to mask up in indoor public settings as the highly contagious delta variant spreads and fuels a rise in COVID-19 cases.

In a joint statement Friday, Santa Clara, Alameda, Contra Costa, Marin, San Francisco, San Mateo and Sonoma counties recommended that all residents, regardless of vaccination status, wear face coverings indoors.

The City of Berkeley, which has its own health department, also joined counties in making the recommendation.

The announcement came amid a spike in COVID-19 cases, most of them the highly transmissible delta variant that has proliferated since California fully reopened its economy on June 15 and did away with capacity limits and social distancing. The vast majority of new cases are among unvaccinated people.

The recommendation in the Bay Area also follows similar announcements made Thursday by health officials in Sacramento and Los Angeles counties.

Yolo County has also urged its residents to mask up for indoor public gatherings.