SACRAMENTO (CBS SF) — California state health officials on Monday confirmed that an alarming increase in COVID-19 case rates would lead the state to reinstitute an indoor mask mandate and other restrictions starting December 15.

Info from CADPH: Renewed Mask Mandate | Travel Advisory 

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The announcement was made during a phone teleconference with California Secretary of Health and Human Services Dr. Mark Ghaly Monday afternoon.

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Ghaly said that in the two and a half weeks since Thanksgiving, California has seen a 47% increase in case rates. He noted that some places like the San Francisco Bay Area and Los Angeles were doing well thanks to higher vaccination rates, but that the dramatic increase was requiring the reinstatement of the earlier indoor mask mandate along with two other COVID protocols.

Only Solano and Marin counties among Bay Area counties don’t currently have an indoor mask mandate in place. The statewide mandate will have much more of an impact outside the region.

The San Francisco Department of Public Health Twitter account later posted that the city would comply with the new requirements for indoor masking going into effect on Wednesday.

“Indoor masking in SF will largely go unchanged, however we are suspending exemptions for work settings and gyms,” the statement said.

Ghaly focused his on public gatherings and admitted there were raised concerns over the Omicron variant, which was first discovered in California at the beginning of the month. That variant and the Delta variant were the driving forces behind the rise in the state’s case rate.

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Ghaly also noted that there was a similar surge last year during the holidays, pointing out that of the 75,000 COVID deaths in the state so far, 20,000 occurred between the week of Christmas through February of 2021.

Beginning later this week on December 15 and extending for one month to January 15, California will institute the following public health restrictions:

1. The state will require masking indoors at all public places. Much of the Bay Area is already under an indoor masking mandate in public spaces except when eating or drinking, though it has become less stringently enforced.

2. At so-called “mega events” where there are more than 1,000 people in attendance, individuals who don’t have proof of vaccination will still be able to attend with a negative COVID-19 test, but results from an antigen test must be within a day of the event. A PCR test must be taken within two days of the event.

Ghaly also recommended that travelers visiting or returning to California take a test within three to five days of arrival in the state. However, that would not be a strict requirement.

“We are already seeing a higher level of transmission this winter and it is important to act now to prevent overwhelming our busy hospitals so we can provide quality health care to all Californians,” state public health director Dr. Tomas Aragon said in a statement Monday afternoon.

At the briefing, Ghaly said Omicron may take over Delta as dominant variant, but it remains difficult to say given variables involved. He said the main problems have been with unvaccinated residents who are still at highest risk of getting hospitalized and dying from COVID.

As of Sunday, health officials said there were 24 confirmed cases of the Omicron variant.

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The California Department of Public Health posted additional information regarding the new COVID protocols on its website Monday afternoon as well as updating the state’s guidance for large events.