The county reported 145 new deaths on Wednesday, the highest one-day total since the start of the coronavirus pandemic.
The county also reported 16,525 new coronavirus cases, the highest number aside from a day earlier this month that included a backlog of older cases.
Dr. Christina Ghaly, director of the county Department of Health Services, warned hospitals are having extreme difficulty dealing with the surge of patients, impacting their ability to treat them as well as deal with non-coronavirus emergencies and surgeries.
She said cases will continue to rise after the holidays. Between Nov. 1 and Jan. 31, the department projects about 8,700 deaths from COVID-19.
"We have never seen daily death rates this high during the course of the pandemic and the model predicts the worst is yet to come," Ghaly said.
"How high those cases go and how overwhelmed our hospitals and health-care workers get - and how many people will die because of COVID, because COVID has pushed all the air out of their lungs and the machines can't push it in anymore - all of that is up to us," Ghaly said.
With Christmas and New Year's approaching, county health director Dr. Barbara Ferrer warned people to avoid gathering in groups and traveling out of the area.
But she acknowledged many are likely to ignore those warnings. For those who do travel out of the county and mingle with others, she urged them to quarantine for 10 days when they return to avoid spreading the virus to others.
The county has at least 6,155 COVID-19 patients hospitalized, although the state estimates the figure at 6,499.
"This coronavirus has upended our lives, our daily routines," Ferrer said. "It's required enormous sacrifices as folks cope with devastating financial losses."
Other details from Wednesday's briefing: