Face coverings are required at San Mateo County facilities starting Monday due to a recent rise in coronavirus cases, county officials said.
The requirement, announced last week, means visitors and county employees will need to wear face coverings at all county offices, clinics or other public facilities, regardless of vaccination status.
Health officials have expressed concerns about the rise of the delta variant of the coronavirus, which is more contagious than the original version.
As of Friday, San Mateo County had reported a total 43,676 cases and 588 deaths since the beginning of the pandemic.
A sharp increase was noted earlier this month: on July 15 county health officials recorded 74 new cases compared to 13 new cases on June 15, the day the state reopened.
Last week, health departments around the Bay Area recommended that everyone wear masks indoors, regardless of vaccination status.
San Mateo County Manager Mike Callagy last week encouraged people to get vaccinated and take common-sense precautions to keep everyone safe.
"The increasing case numbers are a harsh reminder that we are not done with COVID and COVID is not done with us," Callagy said.