The novel coronavirus has badly hurt business at San Francisco’s hotels, along with airport traffic, city Controller Ben Rosenfield said Wednesday at a public hearing.

Some downtown hotel occupancy rates have plunged to around 20% and 30% this week, down from a robust 80% to 85% occupancy rate, the controller said. The drop is driven by the loss of business, leisure and convention travel.

Rosenfield said he expected the fallout to increase in more sectors, like restaurants. With no official estimates yet for total city revenue losses, Rosenfield said they could be in the tens of millions of dollars for the quarter.

“Our hotels are emptying out very quickly,” Rosenfield said, adding that the decline has been worse than in the aftermath of the Sept. 11, 2001, terrorist attacks. The hotel industry employs around 25,000 people in the city.

The city is already facing a budget deficit of $321.4 million over the next two fiscal years, Rosenfield said Wednesday, which is narrower than a previous forecast of $419.5 million. The city’s budget is $12.3 billion, and more than $1 billion comes from business taxes.

The changes are a dramatic shift from 2019, when the city had record leisure and business travelers.

“We haven’t seen something like this in a long, long time,” said Kevin Carroll, CEO of the Hotel Council of San Francisco, which represents hotel owners and operators. “It’s really down.”

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He said that hotels are looking at potential layoffs, but he didn’t have any details.

More pain is on the way. All Moscone Center conventions have been canceled until mid-May, with organizers fearing mass gatherings could spread the coronavirus, resulting in the loss of 235,000 hotel room nights.

The city banned gatherings with 1,000 or more people for at least the next two weeks, which will further boost economic losses.

Airport numbers reflect the drop-off in visitors. City data show SFO landings are down 20% this week for international flights. Domestic landings are down 12%.

Last weekend, city-owned parking garage vacancy rates were between 20% and 40%, with especially low activity in downtown, Civic Center, North Beach and Chinatown.

On Monday, San Francisco BART exits were down 24% from the previous week.

Rosenfield said he expects “very significant” declines in hotel taxes, along with losses in sales tax and parking taxes. He also expects the city treasury’s interest earnings to fall after federal interest rate cuts.

The Board of Supervisors is working on legislation to aid residents and businesses affected by coronavirus, including a moratorium on many residential evictions and creation of a fund to help small businesses pay rent. Mayor London Breed is also allowing small businesses to defer tax payments and some licensing fees.

Carroll said any workforce relief such as expanded state or city unemployment benefits and protection around housing would help hotels endure the downturn, as well as the deferred tax payments.

Roland Li is a San Francisco Chronicle staff writer. Email: roland.li@sfchronicle.com Twitter: @rolandlisf