California recorded a massive jump in coronavirus cases over the long holiday weekend, including an average of roughly 3,400 cases a day from Christmas Eve through Monday in the Bay Area — numbers far outpacing the summer surge as the omicron variant continues its takeover.
The positive test rate, a key marker of how widespread the virus is, skyrocketed to a seven-day average of 9.6% as of Tuesday, according to the California Department of Public Health. That’s up from just 3% one week ago.
The explosive rise in cases prompted San Francisco on Tuesday to cancel its New Year’s Eve fireworks celebration, for the second year in a row. City officials said they were concerned about potential spread of the virus at the event, along with public safety due to many essential workers — including police and fire fighters — being unable to work because they are in isolation or quarantine from COVID.
The state numbers released Tuesday included four days worth of COVID reporting, for a total of 13,454 new cases for the nine-county Bay Area and 86,027 for all of California. They underscore what local health officials have been saying anecdotally for a week: that most if not all of California is well into a new winter surge, fueled by the highly infectious omicron.
“The real substantial jumps came at the end of last week. We’re already seeing case numbers in excess of our worst days over the summer, and I think we’re going to keep right on climbing to the kinds of numbers we at least saw last winter,” said Dr. Nicholas Moss, the Alameda County health officer.
COVID hospitalizations are climbing too, but not nearly at the same rate, and health officials said they remain hopeful that even an astonishing surge in cases won’t result in a flood of severely ill patients. About 4,400 people were hospitalized with COVID in California as of Monday — including 435 in the Bay Area — for a 37% increase from the start of the month.
The United States is reporting average daily new cases close to or even higher than last winter’s surge, according to multiple data sources, including the Centers for Disease Control and Prevention.
California is not yet at its all-time peaks, though cases are growing at an unprecedented clip. A month ago, cases had leveled out in almost all counties, with a daily average of about 4,400 for California and 550 for the Bay Area.
As of Tuesday, the state is now reporting a seven-day average of 8,686 cases a day, according to the California Department of Public Health; Chronicle analysis puts the average higher, at well over 11,000 cases a day. The daily average for the Bay Area is over 2,000.
Last winter, cases topped out in mid January at 45,000 a day for the state and 2,800 for the Bay Area.
“It’s safe to say we’re at levels that exceed even the height of the delta surge back in the summer, and we’re not sure quite how high that’s going to go,” said Marc Meulman, director of public health, policy and planning for San Mateo County.
Meulman said cases are higher than with delta among both vaccinated and unvaccinated residents. And he noted that new cases can take a day or two to show up on county logs, “so things are probably worse at the moment.” Other health officers noted that with more people taking home tests, and some opting not to get tested at clinics due to long wait times, the reported cases are probably well below the actual number of infected people.
Health officials said the current numbers are striking, and far surpassing what they’d expected from a winter surge when delta was dominating. The delta variant — previously the most infectious strain of the coronavirus, but now outmatched by omicron — is likely still spreading, officials say.
On Tuesday the CDC revised down its estimate of omicron’s prevalence in the United States. The agency previously had said omicron likely made up more than 70% of new U.S. cases as of mid December — now it says omicron probably made up only 23% of cases then, and about 60% of cases for the week ending Dec. 25.
That means both omicron and delta are likely in play at the moment, though the ratio probably varies dramatically from place to place.
“It’s almost an academic discussion,” said Moss. “It doesn’t really change what we need to do and it doesn’t change the broad outlines of what we may see this winter.”
Several counties have recently tightened measures meant to prevent transmission amid the omicron onslaught. Santa Clara County on Tuesday joined a few of its neighbors in requiring workers in certain high-risk settings to be boosted. Contra Costa County updated its mask mandate to eliminate exemptions for vaccinated people in certain situations, such as offices and gyms.
Both Santa Clara and Sonoma counties strongly urged private employers to require staff be boosted as well as vaccinated. Dr. Sara Cody, the Santa Clara County health officer, also advised restaurants, bars and other businesses where patrons remove their masks to require customers be boosted.
Studies have shown that boosters are critical to increase protection against severe illness due to waning immunity, especially against omicron.
“Less than two week ago, I warned of a deluge of omicron, and today unfortunately that deluge is here,” said Cody at a briefing Tuesday.
Health officials said the outlook for hospitals remains unclear, though they’re encouraged that so far they’re not seeing a surge in severely ill patients. Moss said hospitalizations in Alameda County are certainly climbing — crossing 100 for the first time since early October. Other health officials said they haven’t yet seen much, or any, increases. Los Angeles County, the state’s most populous, reported Tuesday that hospitalizations had climbed 30% in just one week.
In Alameda County, “We have about two and a half times as many people in the hospital right now as we did in our low point in early December. And it’s climbing daily,” Moss said. “If we see any increases (in severe illness) tied to the kinds of increases in case rates we saw in the last seven days, then our hospitals are going to be feeling the pinch.”
In Marin County, which has the highest overall vaccination rates in California, Dr. Matt Willis, the health officer, said cases have clearly been “uncoupled” from hospitalizations because so many more people have at least some immunity and are developing mild illness.
Though the county is reporting more cases than at any other time in the pandemic, only four people were hospitalized as of Monday — a tenth of the total from the peak of last winter’s surge.
“On Christmas Day we had the highest number of cases ever,” Willis said. “We expect to see some signature of COVID in our hospitals. We will see an uptick, undoubtedly. But it’s so clearly been uncoupled from case rates.”
Chronicle data reporter Nami Sumida contributed to this report.
Erin Allday is a San Francisco Chronicle staff writer. Email: eallday@sfchronicle.com Twitter: @erinallday