SACRAMENTO (AP/CBS13) — Stay-at-home orders in the San Joaquin Valley and Southern California regions, where ICU units are running out of beds, were extended on Tuesday after Gov. Gavin Newsom warned residents to brace for the effect of a “surge on top of a surge” of coronavirus cases from holiday travel.

The order will remain in place as ICU capacity in both regions was at 0 percent, according to California’s top public health official Dr. Mark Ghaly on Tuesday. That means 23 of the state’s 58 counties will remain under the order.

Newsom said that even with admissions to hospitals plateauing in some places, the state was destined to move into a “new phase” that it’s been preparing for as it sets up hospital beds in arenas, schools and tents, though it is struggling to staff them.

“As we move into this new phase, where we brace, where we prepare ourselves for what is inevitable now … based on the travel we have just seen in the last week and the expectation of more of the same through the rest of the holiday season of a surge on top of a surge, arguably, on top of, again, another surge,” Newsom said Monday.

Just this week, nearly 40 health care officials were sent by the U.S. Department of Defense to two San Joaquin County hospitals, Dameron Hospital in Stockton and Adventist Health Lodi Memorial, to assist in the battle against COVID-19.

As of Tuesday, ICU capacities in the other 3 regions in the state were listed on California’s COVID-19 website as 27.9 percent in Northern California, 19.1 percent in the Greater Sacramento region and

State officials also notified hospitals that the situation is now so dire that hospitals should prepare for the possibility that they will have to resort to “crisis care” guidelines established earlier in the pandemic, which allow for rationing treatment.

The current surge of cases is due in large part to Thanksgiving travel and celebrations despite warnings from public health officials not to gather as the state was already in the midst of an exponential growth in cases.

That surge has created the greatest challenge for the state’s health system since the pandemic began and has been regularly breaking records for case counts, hospitalizations and deaths from COVID-19.

While daily coronavirus cases were down to 31,000 Monday from a seven-day average above 37,000, it was likely due to a lag in data from the weekend, Newsom said.

Models used for planning show hospitalizations more than doubling in the next month from about 20,000 to more than 50,000.

The state has several makeshift hospitals – including the Sleep Train Arena which reported over a dozen patients this past weekend – that are taking patients but need more health care workers to staff the facilities, Newsom said.

California has deployed more than 1,000 people to 116 hospitals and other facilities in the state through a volunteer corps or the National Guard. On the upside, Newsom said California finally expects to receive more of the traveling health care workers it had requested in anticipation of the shortage.

The Department of Public Health is sending an emergency medical team to Los Angeles to help better distribute patients among hospitals. Some hospitals are well above capacity and others are below capacity, Newsom said.

Travel over Christmas is anticipated to create another spike in cases that 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 fall sick enough to require hospitalization.

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Dr. Ghaly urged people not to gather for New Year’s celebrations, which would further compound problems in the month to come. He said surveys about a month ago found only 30% of Californians were going to alter plans to gather or travel but more recent surveys show 50-60% changing their plans.

“Things that were, a month ago or two months ago, a low-risk activity today are really high risks because of the level of COVID that’s circulating in our communities,” he said.

Copyright 2020 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.