Dr. Barbara Ferrer said Monday things may get worse before they get better.
"The sad reality is that all indicators tell us that our situation may only get worse as we begin 2021. The rate of community transition remains extraordinarily high," Ferrer said. "This has taxed our hospital system as more COVID-19 patients continue to stream in, on top of the thousands of patients already fighting for their lives."
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L.A. County is quickly becoming the country's epicenter for coronavirus, with the countywide cumulative total at 734,860 cases, 9,564 deaths and 7,181 people hospitalized as of Monday.
Between early November and Saturday, average daily COVID-19 hospitalizations in the county increased by 674%, while daily deaths have jumped by 600%.
Ferrer also stressed her concern over people traveling for the holidays, with Tuesday expected to be the busiest travel day on the roads.
Travel over Christmas was expected to create another spike in cases. It may not show up for several weeks because of a lag from the time someone is exposed to the virus to when they get test results and ultimately get sick enough to require hospitalization.
Although there are indications more people are heeding stay-at-home orders that apply to all of the state but northernmost rural counties, there was a bump in air travel in Los Angeles similar to Thanksgiving.
Over 7 million people went through U.S. airports from Dec. 20 to Dec. 27, the highest level of air travel in more than nine months, despite fear that travel will lead to more cases of COVID-19.
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Overall, air travel is down nearly 60% from this time last year. But the Transportation Security Administration said it screened 1,284,599 on Sunday, the highest total since March 15.
The number of passengers flying out of Los Angeles International Airport was down about 70% from last year between Dec. 21 and 27, but the high of 43,000 on Dec. 23 was only 60% below last year's figures, spokesman Heath Montgomery said. That was about as busy as the airport has been since the pandemic began.
Ferrer also emphasized the anti-gathering message ahead of yet another holiday just days away: New Year's Eve. She said anyone who traveled over Christmas in spite of warnings needs to self-quarantine for 10 days, even if they believe they took precautions.
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"It has been hard to find joy this holiday season, in light of the devastating impact COVID-19 has had on so many across this county,'' Ferrer said. "And the sad reality is that all indicators tell us that our situation may only get worse as we begin 2021. The rate of community transmission remains extraordinarily high, and this has taxed our hospital system as more COVID-19 patients continue to stream in on top of the thousands of patients already fighting for their lives. As cases continue to remain at these alarmingly high levels, hundreds more people are likely to die.''
Los Angeles County, which accounts for a quarter of California's nearly 40 million residents, has about 40% of the state's 24,000 deaths. The county is approaching a milestone of 10,000 deaths.
"These are figures that can't be normalized," county Supervisor Hilda Solis said. "Just like the sound of ambulance sirens, we can't tune this out."
City News Service and The Associated Press contributed to this report.