US health officials warned of a surge after millions of Americans travelled to celebrate last week’s Thanksgiving holiday despite pleas from authorities to stay home.

The staggering increase in cases is leading to fresh lockdown orders in California as the state seeks to prevent hospitals from becoming overrun by Covid-19 infections.

Five counties – encompassing areas including San Francisco, Oakland and much of Silicon Valley – along with the City of Berkeley plan to adopt measures including shutting down personal care services, outdoor restaurant operations and entertainment venues, county health officers said on Friday. The rules will be effective December 6 until January 4.

01:40

US coronavirus: Wisconsin residents queue for hours to get Covid-19 tests as infection rate soars

US coronavirus: Wisconsin residents queue for hours to get Covid-19 tests as infection rate soars

The restrictions aim to closely mirror regional stay-at-home orders imposed by California Governor Gavin Newsom on Thursday, which take effect when availability of ICU beds falls below 15 per cent. While much of the Bay Area has not met that metric, the counties are moving quickly to prevent a deeper health crisis.

“We have little choice but to act and to act now,” said Sara Cody, health officer for Santa Clara County, home of many of Silicon Valley’s tech giants. “We hope that by acting early, and by acting as a region, we’ll have the best chance at bending the curve faster.”

California is struggling with its worst wave of coronavirus cases since the pandemic began, reporting a record 22,018 new infections on Friday. Los Angeles County, the epicentre of the state’s outbreak, adopted stay-at-home rules earlier this week as its hospitals fill. The Bay Area – the first in the US to impose lockdown measures in the spring – has been credited for its relative success in fighting the virus, only to see its outbreak quickly intensify.

Biden asks Fauci to join Covid-19 team as US cases pass 14 million

In San Francisco, cases now average 114 a day, compared with 34 in late October, Mayor London Breed said. Hospitalisation is up 35 per cent in the past week.

Grant Colfax, San Francisco’s health director, said the city had perhaps one week to bend the curve enough that its hospital system will not be overwhelmed. At current rates, the city may run out of intensive care beds the day after Christmas, and by January 4, an estimated 200 people in the city who need a hospital bed will not be able to get one. By February 4, that number could swell to 1,600, he said at a briefing on Friday.

“We have to do everything we can to prevent this from being a holiday season that we look back on as one of sickness and death, especially now that we have vaccinations that are really in sight,” Breed said. “We know that if we wait, we are just delaying the inevitable.”

The rules allow for more movement than the deeper lockdowns earlier in the pandemic. Retail stores can be open at 20 per cent capacity, while outdoor gyms and fitness classes can operate at a maximum of 12 people.

Still, the shutdowns are a fresh blow to businesses just as the holiday season gets under way.

“Today’s move to ‘jump’ the state is very difficult for our industry,” Laurie Thomas, executive director of the Golden Gate Restaurant Association, said in a statement. “The majority of restaurants simply cannot make it financially on takeaway alone.”

On Friday, Anthony Fauci, the top US infectious disease specialist, said the country had not yet seen the “post-Thanksgiving peak,” the full brunt of which he said could be expected in the next week or two.

“We’re in a very precarious situation right now,” Fauci told NBC News. “There certainly is light at the end of the tunnel with a vaccine, but we’re not there yet, so we really have to intensify our public health measures to try and blunt this trajectory.”

The US has recorded more than 14.3 million Covid-19 cases and 278,000 related deaths since the start of the pandemic.

Additional reporting by Agence France-Presse