The Graton Resort and Casino says that it has canceled a private New Year’s Eve party that was expected to draw up to 4,000 guests after health officials publicly raised concerns about whether the event would further spread the virus in the midst of a statewide surge.

Graton officials didn’t have to cancel. The casino, located on tribal land in Rohnert Park, falls under the purview of the Federated Indians of Graton Rancheria, and is not subject to county or state shutdown edicts.

While the casino canceled the controversial event, the venues remain outside health authorities’ purview, among the few buildings in the Bay Area where hundreds of people from different households mix indoors on a daily basis. While offices, museums and restaurants are completely shut down, on any given day, thousands of gamblers statewide head into the smoky, dark interiors of a casino, where they sit at slot machines or play poker at full tables, perhaps grabbing a bite to eat at an indoor restaurant, or sit at a bar sipping a cocktail while watching a basketball game.

Gov. Gavin Newsom’s shutdown order of indoor entertainment venues does not apply to the sovereign tribal lands and most of the state’s 62 tribal casinos have remained open during much of the pandemic, including Graton, Lytton Casino San Pablo and River Rock Casino in Geyersville.

But the New Year’s Eve party worried Sonoma County health officials, who had been in contact with the casino in recent days, Paul Gullixson, Sonoma County communications manager, said before the cancellation.

The current coronavirus surge has pushed many California hospitals to capacity, although in Sonoma County, ICU capacity remains at nearly 24%, well above the Bay Area average of just over 9%.

Still, as cases continue to rise, about 1 out of every 100 people in Sonoma County has an active case of the coronavirus, according to county health officials.

At a casino party of 4,000 people, that would mean about 40 people would be expected to have COVID-19, based on county statistics. The odds of interacting with one at an indoor event would be close to 99%, according to a Georgia Institute of Technology risk assessment tool.

It’s unclear whether there have been outbreaks connected with tribal casinos in California or whether the independent tribes would be required to report any. Cases among a company’s staff or customers would probably be added to county totals rather than connected to the specific business.

Tribal Chairman Greg Sarris said in a statement Thursday that the Graton casino has exceeded all federal safety requirements and would continue to remain open on a limited basis — except on New Year’s Eve.

Instead of hosting a party, the business would shutter at 5 p.m. and reopen at 6 a.m. the next day, Sarris said.

On Christmas Eve, the doors were open, hundreds of cars in the parking lot as a steady stream of public and chartered buses pulled in front, the gamblers filing out and heading to the entrance where they lined up for thermal temperature checks.

Inside, there was a sense of normality amid the artificial coin clanking and shrill bells for minor jackpots, the roving waiters dropping off bottles of beer or other beverages next to the patrons.

Everyone wore a mandatory mask, although they were frequently pulled down for a puff of a cigarette or a sip of a cocktail.

Lisa Vallejos sat at a Dancing Drums slot machine, pushing the spin button again and again and again.

She comes a couple of times a week, taking a chartered bus from San Jose.

“It’s a place to go,” she said. “I’m careful.”

On both sides of her, see-through barriers kept her somewhat isolated from other gamblers, although in most cases, the seats were closer than 6 feet and often, the players would lean back beyond the barrier putting their breath and bodies within spitting distance of strangers.

In the poker room, the tables were full, the five gamblers nearly elbow to elbow although separated by the same transparent barriers. Dozens more were waiting outside for a seat to open.

Just before noon, Emilce Palencia was headed to work at the casino’s rewards center. She started the job five months ago and said all employees are tested once a month, although that will change to twice a month in January, she said.

She doesn’t know anyone who’s gotten the virus at work and said she’s glad it has remained open.

“I absolutely need job security,” she said.

Nearby, Annie Sparks sat at a booth in the casino’s food court while her friend gambled nearby.

“I came for the soup,” she said, motioning to a menu board featuring chicken pho.

She said neither she nor her friend was worried about catching the coronavirus in the casino.

“He’s an old hippie, and he doesn’t really believe in it,” she said. “And I think we’re all going to get it eventually.”

San Francisco Chronicle staff writer Aidin Vaziri contributed to this story.

Jill Tucker is a San Francisco Chronicle staff writer. Email: This e-mail address is being protected from spambots. You need JavaScript enabled to view it Twitter: @jilltucker