Contra Costa, Sonoma, Alameda, and San Mateo counties issued mask orders for health care staff in hospitals and other care facilities. The orders start on Nov. 1 and last until April 30, 2024, officials said, citing recent increases in COVID-19, influenza, and other respiratory viruses that are typically commonplace during the colder months.

"Each year we see that higher rates of influenza, COVID-19 and other respiratory viruses that can cause severe respiratory infections occur annually between late fall and spring," Dr. Karen Smith, the Sonoma County interim health officer, said in a statement last week.

Contra Costa Health Services CEO Anna Roth told the county's board of supervisors last week that the mandate will be enacted, according to local media reports.

"We are issuing the health order today around masking for high-risk facilities, health care facilities specifically," Ms. Roth said. "So again, masking in hospitals, masking in skilled nursing facilities, masking in high-risk facilities."