California is recruiting thousands of retired healthcare workers along with medical and nursing students to help staff emergency hospitals at sites that could include the Los Angeles Coliseum and other sports arenas to handle the anticipated flood of coronavirus patients, Gov. Gavin Newsom said Monday.

Newsom signed an executive order to temporarily expand the healthcare workforce to staff the facilities that will supply the 50,000 hospital beds he estimated could be needed when the surge peaks. State models now estimate the peak occurring in mid-May.

The state will waive certain professional licensing and certification requirements to get workers in the field faster.

"If you're a nursing school student, a medical school student, we need you," Newsom said. "If you've just retired in the last few years, we need you."

The coronavirus is spread by coughs and sneezes. California has more than 7,100 confirmed cases and at least 146 deaths, according to a tally by Johns Hopkins University. In the last four days, hospitalizations have doubled and patients in intensive care tripled to 600, Newsom said.

The state is ramping up testing and health officials say that will bring a big increase in cases. Newsom said shortage of swabs is a "principal limiting factor" in getting even more tests done.

"The number of pending tests out there is extraordinarily frustrating because of the delay in getting that information back into the system, into the patient's inbox,"he said. "Tens of thousands of tests have been conducted, but we do not have the results yet."

The state's largest county, Los Angeles, counted more than 300 new cases and seven deaths in the last day. It will be important this week to see if cases double or triple over short periods to better predict the peak of infections, county Public Health Director Barbara Ferrer said. County officials are predicting a peak at the end of April.

"The truth of the matter is, none of us really know," Ferrer said of the timeline . "We're all making a best guess."

With social distancing measures giving the state time to increase hospital capacity and obtain scarce and much-needed supplies such as ventilators and masks and rubber gloves for healthcare workers, the state was trying to add the personnel necessary to cope with an expected crush of cases.

"We've done nothing more than buying a little time, but we're not spiking the football," Newsom said later in a Facebook chat with founder Mark Zuckerberg and his wife, Dr. Priscilla Chan.

Facebook pledged $25 million to help provide child care, transportation and lodging to the retirees and students who answer the governor's call. They will be paid by the state and provided with malpractice insurance.

The estimated 37,000 who are eligible were asked to register at the California Health Corps website.

Amber Rodriguez, a nursing student at West Coast University registered for the new program shortly after watching Newsom's announcement.

Rodriguez is supposed to graduate in August and has seen her classes cut short, including a hands-on critical care term. She's hoping to get that experience during the crisis when she knows so many medical workers are putting in long hours.

"This may not be the only time that a pandemic happens during our nursing career," she said.

How the state clears the way for students and others to help out — and where they might be assigned — was not clear. Nursing schools have complained that hospitals halted clinical rotations during the virus outbreak and that has prevented students from getting the clinical experience they need to graduate.

"This urgency is why we are left disappointed that there is still no clear pathway forward for the thousands of nursing students who can no longer move forward with their education," said Robyn Nelson, nursing school dean West Coast University.

Veronica Harms, spokeswoman for the Department of Consumer Affairs, said they were working on getting waivers in place to increase the healthcare workforce.

To help prepare for a wave of patients, National Guard troops set up beds in the sprawling Los Angeles Convention Center, converting it from a site that normally hosts meetings, trade shows and exhibitions into a field hospital.

There also were discussions about putting beds at the LA Coliseum, home to the 1932 and 1984 Summer Olympics, as well as the Oakland Coliseum and Sleep Train Arena in Sacramento, Newsom said.

The 1,000-bed Navy hospital ship Mercy received its first patients Sunday after docking at the Port of Los Angeles, where it is intended to ease pressure on hospitals by taking in people with non-COVID-19 ailments.

Newsom's announcement came as San Francisco and five surrounding counties extended stay-at-home orders until May 1. On Sunday, President Donald Trump, bracing for a national death toll that could exceed 100,000, bowed to recommendations from public health experts and extended restrictive social distancing guidelines through April.

Over the weekend, more people appeared to heed the message to stay home after beaches and many parks were closed by state and local officials following a swarm of visitors during the first weekend of California's stay-at-home order.

Still, people continued to crowd some of the open parks. On Sunday, the state expanded closures amid concerns people were not keeping a proper distance from one another. Parking lots at all state parks were closed, and the most popular places were closed to all activities.

A surfer in Manhattan Beach south of Los Angeles was issued a citation that could carry at $1,000 fine for violating orders to stay off the beach. That was an anomaly, however. Most police issued only verbal warnings.

San Francisco's subway and light rail system closed Monday, with service replaced by buses. Rail ridership had dropped by more than 90%.