Health officers in Alameda, Contra Costa, Marin, San Francisco, San Mateo, Santa Clara, Sonoma and the city of Berkeley announced a mask mandate Monday afternoon, requiring every resident to wear a face mask indoors in public settings, regardless of vaccination status.
The health order will go into effect Tuesday at midnight.
The mandate is aimed at reducing the spread of COVID-19 amid a surge in cases and the Delta variant.
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"Across the Bay Area region we are seeing COVID-19 cases surging and hospitalizations are on a steep rise again, particularly among the unvaccinated. In Contra Costa County we're alarmed at the rate at which COVID patients are filling our community hospital beds," said Dr. Chris Farnitano, health officer for Contra Costa County.
He said the number of patients hospitalized in Contra Costa County has doubled in just the past 10 days and increased by more than 400% in July.
"While there may be slight differences between each jurisdictions' orders issued today, they all have one thing in common. A simple step, wearing a mask indoors to provide one more layer of protection for everyone," he said.
Each county emphasized the how the virus is increasingly spreading among the Bay Area's unvaccinated population.
"In Sonoma County, our case rate for unvaccinated individuals is nearly six times higher than it is for our vaccinated population," said Dr. Sundari Mase, health officer for Sonoma County. "This is not the same virus that we were combating last year, even a few months ago. The Delta variant is 60% more transmissible than previous versions of the coronavirus, and (we have) an increase in the number of vaccinated people now testing positive."
VIDEO: Bay Area health officers address mask mandate, Delta variant, COVID-19 testing
Health officers from the seven counties implementing the mask mandate emphasized the effectiveness of masks, particularly in indoor settings.
"The virus doesn't care what kind of indoor space you're at, whether it's in a public building, or someone's home. Anytime you're in an indoor space with other people who you don't live with, there is a risk that you could get infected with the virus that causes COVID-19," said Santa Clara Deputy Health Officer Dr. George Hahn.
As cases rise, several Bay Area counties said they've also seen an increase in demand for COVID-19 testing.
"In Contra Costa County we have seen an increased demand for testing and we are working with our local labs, and have we opened up contracts with additional labs to make sure that we have the lab capacity to do this testing, as well as a testing site capacity," said Dr. Farnitano
The Bay Area isn't the only region in California with a mandatory mask mandate.
Los Angeles County reinstated its mask mandates in July.
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Napa and Solano counties are now the only two Bay Area counties not included in the latest indoor mask mandate.
In a statement to ABC7, a spokesperson from Solano County said, "Solano County Public Health and the state monitor the spread of COVID-19 in our community, we will continue to align with state recommendations. We are following emerging data and science, and we will adjust our approach as needed."
Solano County said the "vast majority" of cases are transmitted at parties, barbeques, picnics and other gatherings, primarily among the unvaccinated and residents in their 20s to 40s.
"Adding restrictions on businesses does not align with our data since the virus spread is predominantly happening at home and in private social settings and not in businesses," the county statement read.
The Bay Area health order comes less than a week after California recommended all residents wear a mask indoors, even those who are vaccinated.
The state's recommendation followed similar guidance from the U.S. Centers for Disease Control and Prevention last Tuesday, recommending that even the vaccinated wear masks in areas where the virus is spreading more rapidly.
According to the California Department of Health, more than 90% of California's population resides in areas with "substantial or high transmission" of the Delta variant.
In the Bay Area, four counties are seeing "high" rates of transmission. This includes Alameda, Contra Costa, San Francisco and Solano counties.
The five other Bay Area counties have what is considered "substantial" transmission.
CDC COVID-19 Transmission Categories by California County
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