A second California county has said that mask mandates will soon be reimplemented in health care settings because of an anticipated increase in respiratory viruses.

Sonoma County interim health officer Dr. Karen Smith said the mandate will go into effect on Nov. 1 and end after March 31, 2026, following a mask mandate that was issued in Santa Cruz County earlier this month.

Because of “the greater risk of COVID, flu and other respiratory virus-related illnesses over the fall and winter months,” Sonoma County issued an order on Oct. 6 that requires health care staff and others to wear face coverings “inside patient care areas of specified health care facilities.”

The order affects skilled nursing facilities, portions of long-term care facilities where nursing care is provided, acute and non-acute rehabilitation facilities, infusion centers, and dialysis centers, according to a county statement.

Smith said the decision was made to lower the “risk to vulnerable patients of COVID, flu, and other respiratory viruses in health care facilities,” adding that the county’s health agency has issued masking orders for specified personnel in health care settings since 2017, three years before the pandemic.

Days before that, Santa Cruz County announced that it was imposing a mask mandate starting Nov. 1 and lasting until March 31, 2026, for people in acute care facilities, skilled nursing facilities, surgical and maternity centers, and infusion centers such as dialysis and chemotherapy centers, during respiratory virus season—not including patients.

“These respiratory viruses can cause serious illness, particularly in vulnerable groups such as infants, older adults, pregnant individuals, and those with weakened immune systems,” Lisa Hernandez, the Santa Cruz County public health officer, said in a statement. “This order aims to reduce the spread of these viruses and protect those most at risk from severe outcomes, including hospitalization and death.”

Last year, officials in counties in California’s San Francisco Bay Area implemented similar mask mandates in health care facilities from November 2024 until April 2025.

In its most recent update issued last month, the Centers for Disease Control and Prevention said 19 states are experiencing “high” or “very high” wastewater levels of COVID-19. Connecticut, Delaware, Nevada, and Utah are seeing the highest levels.

“COVID-19 activity has peaked and is declining in many areas of the country, but emergency department visits and hospitalizations are elevated nationally,” the CDC said in a separate statement.

The CDC says on its website that because of the ongoing government shutdown, some information posted by the agency may not be up to date and that CDC staff may not be able to respond to media inquiries.

Studies have shown that face coverings have had little to no effect on the spread of COVID-19. The CDC previously touted studies supporting the practice and backed a study saying that masks “effectively filter virus-sized particles in laboratory settings” and that “use of respirators with higher filtration capacity was associated with the most protection, compared with no mask use.”