Los Angeles County could be seeing the beginning of another COVID-19 winter surge, the county’s health director warned Thursday.

Last year’s winter surge was unprecedented. The virus exploded countywide, breaking case number records as the health care system buckled under the pressure, morgues filled up and refrigerated trucks were brought in to deal with a “backup of dead bodies.”

Now, a year later with vaccines available, health officials hope the county won’t be as hard-hit.

The signs of another approaching winter surge are beginning to show: the region’s estimated weekly coronavirus case rate now stands at 113 new cases per 100,000 residents, putting the nation’s most populated county back in the Centers for Disease Control and Prevention’s “high transmission” category for COVID-19.

The jump in transmission levels also comes as hospitalization numbers begin to creep up. There were 666 people hospitalized with COVID-19 Thursday, an increase of 93 people over the past week.

“We do expect increases to continue on the heels of our Thanksgiving gatherings. But already, based on the trends, we are looking at the possible beginnings of a winter surge,” L.A. County Health Director Barbara Ferrer said in a Thursday media briefing.

In the week after the Thanksgiving break, the number of infections also increased at schools, rising to the highest level since late September.

“If, as we suspect, this increase in cases reflects transmission that took place during holiday gatherings, we should consider this an early warning about the upcoming December holiday,” Ferrer said.

Ferrer said any increases in COVID-19 numbers are “worrisome,” especially since the county has moved from having “substantial” transmission back to “high” transmission.

“I’m never going to downplay what’s going on when we start seeing these increases,” Ferrer told members of the media, during one of her weekly COVID-19 news briefings that she has been holding for nearly two years.

Still, the health director noted that the county is better off than it was during the last winter, before vaccines were available.

So far, 68% of L.A. County residents aged five and older are fully vaccinated. Around 77% have received at least one dose.

The vaccinations are making a difference, Ferrer said.

“It particularly is making a difference in preventing us from experiencing the devastating crisis we had in our health care system,” she added.

While L.A. County is seeing increased virus spread, most people who are fully vaccinated will not end up with serious illness if they catch the virus.

The availability of vaccines means that fewer people are expected to be admitted to hospitals this winter than last, but ongoing staffing shortage issues at many of L.A. County’s hospitals has health officials worried.

The county is faced with the possibility of a winter surge just as it comes out of the summer delta coronavirus variant surge and begins documenting cases of the worrisome new omicron variant.

Five cases of the omicron variant have so far been found in L.A. County, and the latest infection appears to be the result of local transmission rather than travel.

“I am urging residents to take advantage of the tools that we have, that we know we didn’t have last year, and contributed to the devastating number of deaths we saw last winter,” Ferrer said. “There’s a lot we all need to do to slow down transmission, and that we’re obviously not all doing.”

“Please don’t wait any longer,” Ferrer said. “The boosters are essential.”