You'll need to put your masks back on in gyms, offices, and places of worship in San Francisco and Contra Costa counties, and other counties with similar exceptions in place since October are signaling similar moves.

San Francisco health officials announced Wednesday that it is pulling back on the mask-order amendment in place since October that allowed for masks to come off in offices, gyms, and places of worship — as well as gatherings where everyone provided proof of full vaccination. Like so many weeks in 2020, when the dynamics of the pandemic led to rules being rescinded and a daily-changing public health picture, this is another one of those weeks.

"Time and time again throughout this pandemic, San Francisco has led the way in fighting back COVID-19," Mayor London Breed tweeted upon the announcement Wednesday. "We can — and we will — do it again."

Encouraging everyone to get a booster if they haven't already, Breed added, "I’m proud that San Franciscans understand public health, know how to make smart choices, and do what’s necessary to protect yourself, your family, and your community."

San Francisco's new order takes effect at midnight tonight and runs through January 31 — and in addition to once again requiring masks in offices and gyms, etc., it requires vaccine booster shots for all workers in healthcare and high-risk settings by February 1. The order also requires hosts of indoor "mega-events" of more than 1,000 people to require proof of boosters for all patrons and staff who are eligible to receive one, starting February 1.

Contra Costa County announced Tuesday that it was rescinding a health-order amendment from October that allowed such masking exceptions. Effective as of midnight last night, masks are required in indoor public spaces countywide with no exceptions — and this includes masks for performers and public speakers at public events and shows.

As NBC Bay Area reports, Marin County is expected to announce a revision to its face-mask order on Wednesday. And Alameda County health officials have indicated that they are reviewing that county's current mask order as well.

Earlier this month, California health officials announced a new statewide mask mandate effective until January 15, as the Omicron surge was just beginning in the state. It was the first such mandate since a statewide rescinding of all mask orders on June 15, 2021 — but most Bay Area counties reinstated their mask mandates by early August amid the Delta surge.

Just a day after the statewide mandate was reinstated, officials made exceptions for Bay Area counties with exceptionally high vaccination rates and relatively low hospitalizations — which included Marin County, where the mask order was broadly lifted in November, and San Francisco, Alameda, and Contra Costa counties, which have been allowing masks to come off in churches, mosques, gyms, and other limited settings.

"The omicron variant is very contagious, and we now know that anyone, regardless of vaccination status, can spread this variant to other people," said Dr. Ori Tzvieli, Contra Costa County deputy health officer, in a statement. "We anticipate the case rate and hospitalization numbers to increase over the coming weeks. To reduce spread, cases and hospitalizations, we all need to wear masks anytime we are in an indoor public setting."

As of Wednesday, San Francisco's daily new case rate continued its vertical rise, and the seven-day rolling average of new cases rose far above the peak of the Delta surge to 616 — with case counts from recent days still not yet reported. As of the SF Department of Public Health's published chart, which only includes reliable data up through December 21, the seven-day rolling average of cases was already eclipsing the Delta peak as of eight days ago.

Rolling average only includes data through Dec. 21. The average as of Dec. 24 was over 600.

While the Omicron variant shows signs of causing milder illness overall, especially among the vaccinated and boosted, solid data on how it will impact the population is not yet available. As SFist reported Tuesday, hospitalizations are ticking up statewide and in the Bay Area, but we will need to wait perhaps another week before we see if this surge in cases is reflected in a commensurate hospitalization rate.

Previously: SF Sees Four Consecutive Record-Breaking Days of COVID Cases; Hospitalizations Rise Across State

Photo: Danielle Cerullo

This post has been updated to reflect San Francisco's announcement.