In late June, Mailinh Nguyen worked two 12-hour shifts as a certified nursing assistant at Fountain Valley Regional Hospital in California's Orange County, looking after the same patient each night. After the second shift, Nguyen said, a supervisor told her that the patient had tested positive for COVID-19.

Nguyen worried that she'd been exposed, because the only personal protective equipment she wore during those shifts was a surgical mask. However, she said, the hospital instructed her to continue working as usual, until she developed symptoms of COVID-19 two days later. Then the hospital placed her in quarantine but told her that she couldn't get tested for the coronavirus at the hospital — she had to go to a community testing site, instead, she said.

"After that, I didn't get paid for over two weeks I was quarantined," said Nguyen, who returned to work after having tested negative.

Workers at Fountain Valley have repeatedly raised alarms in recent weeks about hospital practices they fear leave them vulnerable to the coronavirus — including lack of testing, reuse of personal protective equipment and subpar infection controls — by writing to the CEO, calling lawmakers and staging two demonstrations outside the hospital. In July, the National Union of Healthcare Workers, which represents employees like Nguyen, submitted a complaint to the California Department of Public Health, which the union said prompted an investigation that continues. (The department said that complaints are confidential and that it couldn't comment on any investigations.)

"It's pretty crazy that major league baseball players have access to testing every other day, but nurses, certified nursing assistants, respiratory therapists — folks that are really in it caring for people that have COVID — can't get tested at all," said registered nurse Jessica Early, a patient policy advocate for the union.

did not address specific employees' complaints. The hospital said it has followed state and federal guidelines to protect workers and patients and that it asks staff members to fill out a daily COVID-19-related screening questionnaires. The hospital confirmed that it sends employees to community testing locations rather than allow them to get tested at the hospital, which is not a public testing site.

"We take immense pride in the extraordinary professionalism and dedication our physicians, nurses and other staff have demonstrated every day in caring for our COVID-19 patients," the hospital said in a statement. "This work has not been easy, but they have risen to the challenge."

At least 29,260 health care workers in California have contracted the virus, and 143 of them have died; nationally, there are 138,626 confirmed cases and 637 deaths among health care workers, according to tracking by the state and the Centers for Disease Control and Prevention.

Up and down California, where COVID-19 cases spiked through July and into August, health care personnel in hospitals say they're facing working conditions that leave them vulnerable to the coronavirus. Health care workers and their unions have tried to improve their situation facility by facility — one even held a five-day strike at a Santa Rosa hospital last month — but they have made little headway. Six months into the pandemic, they say they are still forced to reuse protective equipment and are denied testing by their own hospitals. Now, many say they need government intervention.

The National Union of Healthcare Workers has asked the state government to issue new rules requiring testing of all newly admitted hospital patients for COVID-19, as well as baseline and exposure-driven testing of health care personnel. Sal Rosselli, the union's president, said it presented its plan recently to Gov. Gavin Newsom and other top state officials, who seemed receptive. (Newsom's office didn't respond to a request for comment.)

"No provider was ready for this pandemic — it was chaos, and it continues to be very chaotic," Rosselli said. "But the fact that workers that treat these patients every day or clean their rooms can't get tested even when they have symptoms, or even when they're exposed, is the demonstration that this industry is driven by profit and not by providing adequate care."

Nguyen's case is one example cited in the union's complaint against Fountain Valley. Another relates to a radiology aide whose immediate family members contracted the coronavirus.

On June 16, the radiology aide says, he told management about his exposure to his ill relatives. According to the union, the hospital told him to continue working as usual, interacting with co-workers and transporting patients around the facility.

Nine days later, he tested positive for COVID-19 and was admitted to the hospital, according to the complaint the union filed with the state. He had potentially exposed an unknown number of patients and other employees to the coronavirus, the complaint states, but the hospital didn't do comprehensive contact tracing.

The radiology aide's colleagues learned of his coronavirus infection when they saw him being admitted to the emergency room, said Joshua Jesus, a radiology technician, who worked with the aide. The hospital's management and human resources offices haven't explained their contact tracing policies, Jesus said.

Fountain Valley said it has had ongoing conversations with the union about employee concerns, and that it follows CDC guidelines to notify staff members about exposures "if they did not wear their PPE appropriately and had prolonged close contact" with a patient.

Contact tracing is a labor-intensive ordeal in hospitals that can have three dozen departments, and that's just one of several barriers to the safety measures unions have demanded. The limited availability of protective equipment has made it necessary to lock up supplies so hospitals don't run out of them. And hospital executives say they have only a limited capacity to process coronavirus tests in-house, so many prioritize patients over staff members who have been exposed but aren't showing symptoms.

"With some of the issues hospitals are facing, they may decide it might be better to let someone quarantine at home and assume they have it," said Mark Brown, chief nursing officer at Good Samaritan Hospital in San Jose, which offers tests to all employees who want them.

Other hospitals in the San Francisco Bay Area have also tested their workers. The Stanford Medical Center in Palo Alto tested about 17,000 employees from March to May and has performed 13,000 additional tests on workers in the summer. The County of Santa Clara Health System performed over 10,000 tests of employees from three public hospitals from late April to mid July to catch asymptomatic carriers.

But those are outliers in the state.

Part of the problem, said Dr. Jahan Fahimi, an emergency care physician at the University of California, San Francisco Medical Center, is that there's no national testing strategy.

"And as a result," Fahimi said, "every county, every health system has been left to come up with their own strategy. That has a few downsides — one being that you have to make tough decisions about allocations of what becomes a scarce resource. In an ideal world, we'd be doing surveillance testing on an ongoing basis — a rotating schedule for all health care workers to catch positives before they care for other patients."

Health care workers outside California interviewed by NBC News say they're encountering similar barriers. A nurse in Kansas City, Missouri said workers are allowed only one N95 mask per day. A nurse in Miami said her hospital refused to even provide the number of staff members who have tested positive. The Washington State Nurses Association said it went to the state's Department of Health for the information to no avail; the department said hospitals haven't provided it with the number of health care workers infected with COVID-19.

Hospitals in New York faced similar complaints from nurses during the surge of COVID-19 cases in April — which should have spurred hospitals elsewhere to implement protections for their health care workers, nurses said.

A survey of 21,200 nurses by the National Nurses United union in July found that 87 percent have had to reuse personal protective equipment, half say their hospitals are trying to clean single-use masks and only a quarter believe their employers provide safe workplaces.

The likelihood of testing positive for the coronavirus increased for front-line health care workers who had to reuse protective equipment, a study published July 31 found. That has a disproportionate impact on Black, Latino and Asian health care workers, the study showed, because they were more likely to have inadequate personal protective equipment.

Coronavirus safety protocols elsewhere in the country are largely up to each hospital; few states have issued rules dictating the steps medical facilities must take to protect front-line health care workers. Instead, hospitals have figured it out on their own, drawing on nonbinding guidance issued by the CDC. Some medical professionals say that has largely left them to fend for themselves.

"It takes me back to the days when I used to take care of an AIDS patient, and I would not know I had an active AIDS patient until I walked in the room and the patient told me," said Lynda Pond, president of the Oregon Nurses Association, who said multiple hospitals in the state have declined to inform staff members when patients they cared for tested positive.

Pennsylvania took a different approach.

The Pennsylvania Department of Health ordered hospitals to inform staff members within 24 hours of exposure to a confirmed or probable case of COVID-19, to test those employees upon request and to replace masks when workers determine they're damaged or otherwise ineffective. The department said it implemented the order after it got complaints about workplaces from health care personnel.

In California, hospital workers hope Newsom, the governor, will issue similar rules, because as it stands, rules about who should be tested in hospitals are "virtually nonexistent," said Early, of the National Union of Healthcare Workers.

"That's a very big risk to both patients and health care workers," Early said. "This lack of regulation is allowing hospitals carte blanche."