For context, the county two weeks ago was averaging 4,200 new cases per day, but this week's average is 10,200, said Public Health Director Barbara Ferrer.
"We're in uncharted territory at this point,'' Ferrer said at an online briefing. "We're seeing daily numbers of cases and hospitalizations that we've not experienced and frankly did not anticipate. Our intensive care unit capacity continues to drop.
"We're on a very dangerous track to seeing unprecedented and catastrophic suffering and death here in L.A. County if we can't stop the surge."
Ferrer asked all residents of the county to stay home as much as possible.
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The nearly 14,000 new cases reported Friday gave the county a cumulative total of 501,635 since the start of the pandemic. By comparison, no state in the U.S. reported a higher number of new cases on Thursday: 12,211 were confirmed in Texas and 12,700 in Pennsylvania.
The death toll also grew Friday, with L.A. County announcing 50 more fatalities.
Hospitalization numbers also continued an alarming climb, with the county reporting 3,624 people being treated for the coronavirus, and 23% of those people, or about 830, were in intensive care.
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Ferrer said if current trends continue, the number of coronavirus patients hospitalized and in intensive care could double in two weeks - a troubling circumstance given the roughly 2,100 available adult ICU beds in the entire county.
"The impact of these Thanksgiving surges of cases, on top of already rising cases, is creating extraordinary stress" on the county's health care system, Ferrer said. "We cannot undo what's already been done. And collectively we're going to all pay a very high price for the actions we were taking in the past."
City News Service contributed to this report.