As a new surge of COVID-19 mounts across the country, Bay Area health officials are returning to their lockstep strategy in hopes of heading off the virus.

On Friday, with hours left for restaurants in San Francisco to cease indoor operations under an order announced earlier this week, Santa Clara, Contra Costa and Marin counties joined in the ban on indoor dining, in addition other new local restrictions.

People gathering indoors, often from different households, and removing their facial coverings to eat and drink, can make for a conducive environment for the virus to spread, according to health experts. But for an industry trying to stay afloat, many stakeholders have said takeout and outdoor service, especially in the winter months, will not be enough.

Local health officials called the recent uptick in cases concerning and said immediate action was necessary.

“We know that eating indoors without masks is a very high-risk activity, and as we close indoor dining we also strongly urge people not to eat or gather indoors with anyone outside their own household,” Dr. Sara Cody, the Santa Clara County health officer, said in a statement. “We must come together as a community and act now to get the virus under control.”

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“Indoor interactions at restaurants, movie theaters, and indoor gyms and fitness centers are high-risk activities,” Dr. Chris Farnitano, health officer for Contra Costa County, said in a separate news release. “And given what we’re seeing happen across the country and the region, we must act now.”

The orders from its Bay Area neighbors come three days after San Francisco announced a similar rollback. Those new restrictions take effect at the end of Friday night, while the ones in Santa Clara and Contra Costa counties will go into effect Tuesday.

The new orders include the region’s most-populous county and its most densely-populated city. Altogether, about half the population of the Bay Area — nearly 4 million people — will face new restrictions.

In addition to the closure of indoor dining in Contra Costa County, fitness centers will be required to shut down indoor operations and concession stands at movie theaters must close.

In Santa Clara County, officials expect to be re-assigned to the more restrictive red reopening tier on Tuesday and, rather than wait, will immediately begin to implement those restrictions. Whereas gyms will close in Contra Costa County, they can remain open at 10% in Santa Clara County but bars and entertainment centers must close entirely, and wineries will be permitted to offer outdoor service. Retail and other essential businesses must limit their capacity to 50%.

Cody referenced an epidemiological curve that began to point “straight up” beginning in the first few days of November.

“It’s the steepness of that curve that concerns all of us and requires us to act swiftly,” Cody said at a news conference Friday afternoon.

Earlier this week, officials in Marin County had “recommended” that restaurants reduce their capacity to from 50% to 25% but that swiftly evolved into a full shutdown of indoor operations; other guidelines are consistent with those in the state’s red tier.

“We’re choosing to move into the red tier before the state moves us to get in front of this surge,” Dr. Matt Willis, the Marin County health officer, said in a statement. “We’re seeing more people getting sick with COVID-19 and needing hospitalization. With flu season and potential impacts from holiday gatherings and travel, it’s time to act to prevent a much larger surge.”

While officials in Alameda County on Thursday announced a “pause” to their reopening efforts, no additional restrictions were placed on indoor businesses, which can still operate at 25% capacity. Similarly, San Mateo and Solano counties haven’t issued any new orders; Sonoma County remains under the most restrictive guidelines set by the state.

In Oregon, which joined with California and Washington in advising a 14-day quarantine for incoming travelers, Gov. Kate Brown on Friday announced a “two-week freeze” that would shut down a swath of indoor activities, including dining, across the entire state.

California’s top health official dismissed any new sweeping statewide orders. Dr. Mark Ghaly said the state’s tiered reopening system allowed for more precise and scientifically guided closures but called the situation fluid.

“We are not looking today at a statewide stay at home order,” Ghaly said. “We know many Californians are fatigued and tired.”