A month ago, the Bay Area was booming. Now, layoffs are mounting at a speed that is catching business owners and employees off guard.

Truckers, cashiers, stagehands, airline workers, party suppliers and countless others are bearing the terrible economic cost of the coronavirus pandemic. And there’s no end in sight.

Some companies are implementing hiring freezes or cutting contractor hours in the hopes the storm will pass and they will be able to hold on to employees once business returns to normal. Some are forced to shed workers.

“This was something I never wanted to do,” said Mike Seramin, owner of party supply company Abbey Party Rents in Daly City, who told his 70 employees Thursday that one-third of them would be laid off. He’s seen 80% of his business canceled for the next three months, equating it to roughly $380,000 in losses.

“There is no way I can sustain a business with almost no money coming in, and the only fair thing to do was let my employees know,” he said. The rest of his workers have been placed on a “staffing hold,” or working from an on-call basis.

Caterers are also feeling the pain. Gov. Gavin Newsom has said events of more than 250 people should not take place, while San Francisco has banned gatherings of more than 100 people.

“We have nothing on the books for two weeks,” said Anna Intertas-Barr, one of the owners of Above and Beyond Catering in San Francisco. She said she laid off a dozen of her roughly 50 employees and stopped hiring on-call caterers as the virus shrank business. She said her company usually generates $250,000 to $300,000 in revenue each month, and she hopes that April events on the books will stay there.

“We have (events) in the beginning of April, but you just never know,” Intertas-Barr said.

San Francisco hotel occupancy rates have plummeted to 20% from 80% a week ago, according to the City Controller’s Office. Restaurants, too, have seen business plunge.

Larrilou Carumba is a housekeeper at the Marriott Marquis in downtown San Francisco and says all of her shifts have been cut, preventing her from getting a place of her own for her and her three children.

“Last Thursday, I have one day scheduled,” said Carumba, a single mom who shares a room in her sister’s house with her children. “Last Monday, they told me that I need to stay home.”

Carumba said she had an apartment in San Leandro lined up, but had to back out when her income suddenly disappeared. She said she is hopeful her union, Unite Here Local 2, will be able to negotiate with the hotel for continued health care and sick time while work dries up because of the virus.

Marriott did not immediately respond to calls and emails requesting comment.

Roughly 3,000 of the union local’s hotel, event and banquet workers are out of work, and that could double within two weeks if occupancy continues to fall, according to Rudy Gonzalez of the San Francisco Labor Council. The Teamsters Local Union 856, which represents hotel front-desk and office workers, has 200 workers idle, and that could double soon also, according to Gonzalez.

California is looking to support small businesses through its Office of the Small Business Advocate by offering access to capital programs like special disaster assistance, according to an email from Lenny Mendonca, Newsom’s chief economic and business adviser.

Mendonca said the state also has a broadly written sick leave policy that covers preventive leave, and that some businesses have voluntarily extended paid sick leave to their employees.

Along with hospitality, the entertainment industry has been hit hard as well. The IATSE 16 stagehand union, which works at theaters, Moscone Center and event venues, has approximately 2,000 members out of work, Gonzalez said. About 500 members of the ticketing and box office union are not working, and the local sign and display union also has approximately 600 people idle, Gonzalez said.

The IBEW electricians Local 6, which usually works at Moscone Center, has 50 to 100 workers unable to do their jobs. A Teamsters union, Local 2785, which handles loading and unloading, has seen 130 members go without work, and the musicians union has 1,400 sidelined, Gonzalez said.

At the Port of Oakland, GSC Logistics, which President and CEO Scott Taylor said handles about 12% of imported merchandise at the port, has cut back on its use of contractors as business and imports have fallen.

“The volume of containers we handle on a weekly basis is down 40% this week,” Taylor said, adding that translated to about half the normal work for his network of 200 independent owner-operator truck drivers. Taylor hasn’t laid off or cut the hours of any of his 100 full-time staff members, and has used the time to further train them, but he said that can go on only so long. He expects the volume of containers to stay down through next week, but is optimistic for the future.

“What we’re seeing on the water and being transported from Asia, primarily China ... is starting to increase,” Taylor said.

Other companies are also trying to insulate workers from the full economic pain of the virus.

Van-rental company Bandago has locations in San Francisco and Oakland and is using revenue from its other locations across the country to keep paying Bay Area staff, according to CEO and founder Sharky Laguana.

“We don’t really have the business coming in to justify the level of employment we currently have,” Laguana said, adding that he had not cut staff and that he sees employees as family. He said he wants his workers to be able to cover basic expenses and that he is trying to determine the best way to do that.

“That assessment has to be made hour by hour,” Laguana said.

For party rental companies, the hour-by-hour assessment keeps getting worse. Schools are closing, universities are moving online, companies are canceling conferences, and even weddings are shrinking drastically. Paper Plus, one of the last party supply stores in Berkeley, is considering layoffs.

In San Francisco, SF Party began closing its store one day a week to cut staffing costs.

SF Party store manager Justine Weathers said business is so rough that she’s scheduling her six employees for six to eight hours of work per week instead of the regular 15 to 32 hours.

“I’ve never had to worry about counting hours for my staff before,” Weathers said. “It all happened so suddenly. One week we were fine, the next week we were not.”

Shwanika Narayan and Chase DiFeliciantonio are San Francisco Chronicle staff writers. Email: shwanika.narayan@sfchronicle.com, chase.difeliciantonio@sfchronicle.com Twitter: @shwanika, @ChaseDiFelice