The unions representing the nation’s health care workers have emerged as increasingly powerful voices during the still-raging pandemic.

With more than 100,000 Americans hospitalized and many among their ranks infected, nurses and other health workers remain in a precarious front line against the coronavirus and have turned again and again to unions for help.

“It’s so overwhelming. It’s unlike anything I’ve ever seen before,” said Erin McIntosh, a nurse at Riverside Community Hospital in Southern California, a part of the country that has been among the hardest hit by a surge in cases. “Every day I’m waist-deep in death and dying.”

In her hospital’s intensive care unit, McIntosh said, nurses have sometimes cared for twice as many patients. “We’re being told to take on more than we safely can handle.”

Her union, the Service Employees International Union, and another union, National Nurses United, which has a powerful presence in California, have pushed back against the state’s decision to let hospitals assign nurses more patients during the crisis.

HCA Healthcare, the for-profit hospital chain that owns Riverside, responded that it had recruited additional nurses and was keeping its employees safe.

Health care workers say they have been bitterly disappointed by their employers’ and government agencies’ response to the pandemic. Dire staff shortages, inadequate and persistent supplies of protective equipment, limited testing for the virus and pressure to work even if they might be sick have left many workers turning to the unions as their only ally. The virus has claimed the lives of more than 3,300 health care workers nationwide, according to one count.

“We wouldn’t be alive today if we didn’t have the union,” said Elizabeth Lalasz, a Chicago public hospital nurse and steward for National Nurses United. The country’s largest union of registered nurses, representing more than 170,000 nationwide, National Nurses was among the first to criticize hospitals’ lack of preparation and call for more protective equipment, like N95 masks.

Despite the decades-long decline in the labor movement and the small numbers of unionized nurses, labor officials have seized on the pandemic fallout to organize new chapters and pursue contract talks for better conditions and benefits. National Nurses organized seven new bargaining units last year, compared to four in 2019. The SEIU also said it has seen an uptick in interest.

Nurses across the country from various unions have participated in dozens of strikes and protests. National Nurses held a “day of action” Wednesday with demonstrations in more than a dozen states and Washington, D.C., as it starts negotiations at hospitals owned by big systems like HCA, Sutter Health and CommonSpirit Health.

Hospitals claim the unions are playing politics during a public health emergency and say they have no choice but to ask more of their workers. “We are in a moment of crisis that we’ve never seen before, and we need flexibility to care for patients,” said Jan Emerson-Shea, a spokesperson for the California Hospital Association.

At the University of Illinois Hospital in Chicago, the deaths of two nurses from the virus helped galvanize employees to strike for the first time last fall, said Paul Pater, an emergency room nurse and union official with the Illinois Nurses Association. “People really took that to heart, and it really fomented a lot of disdain for the current administration at the hospital.”

In their most recent contract, nurses there won provisions ensuring the hospital would hire more staff and keep sufficient supplies of protective equipment, Pater said. “We’ve been able to make, honestly, just huge strides in protecting our people.”

The hospital did not respond to requests for comment.

Some nurses remain highly skeptical of the unions’ efforts, and even those who favor organizing acknowledge there are serious limits to what they can accomplish. “I’m not sure that the union is enough because it can only take us so far” since staffing conditions remain overwhelming, said McIntosh, the Riverside nurse.

Many health care workers view vaccines as the beginning of the end of the pandemic. But large numbers—especially those who work in nursing homes and outside hospitals, who tend to have higher rates of vaccine hesitancy—are refusing to be immunized. During a crisis that disproportionately threatens health care workers of color, one recent analysis found that they are getting vaccinations at rates far below those of their white colleagues.

The unions find themselves treading a fine line between encouraging their members to get vaccinated and protecting them against policies that would force them to do so.

“There are still unanswered questions,” said Karine Raymond, a nurse at Montefiore Medical Center in the Bronx and a New York State Nurses Association official. “The union believes that all nurses should seriously consider being vaccinated,” said Raymond, who would not say whether she personally would accept the vaccine. “But, again, it’s the individual’s choice.”

The nurses and their unions do want to keep pressuring employers to safeguard workers and patients. “Just because a vaccine is rolling out doesn’t mean that we can let up on other important protections,” said Michelle Mahon, a National Nurses United official, during a Facebook Live event last month.

The past year has created conditions ripe for organizing to address long-standing issues like inadequate wages, benefits and staffing, a problem exacerbated by health care workers falling ill, burning out or retiring early for fear of getting sick. The unions “have successfully been able to use the pandemic to rebrand those same conflicts as very urgent safety concerns,” said Jennifer Stewart, a senior vice president at Gist Healthcare, a consulting firm that advises hospitals.

They have also shifted many nurses’ view of their employers, she said. “The perceptions and the experiences are being crystallized and starting to be viewed through a certain lens. And I think that lens is very favorable to unions.”

At Mission Hospital in Asheville, North Carolina, safety concerns created by the pandemic added urgency to the nurses’ push to join forces with National Nurses United.

Some questioned the union’s ability to deliver better working conditions and raised concerns about the union creating divisions within the hospital. A group of 25 Mission nurses signed a letter before the vote saying “an outside third party, like the NNU, is not the solution.”

But last September, 70 percent of nurses approved the union, one of the largest wins at a hospital in the South in decades. Susan Fischer, a Mission nurse who helped lead the organizing drive, called National Nurses United “instrumental in helping us find our voice.”

She said the union was already proving its worth, pushing management in bargaining talks this month to provide better access to protective equipment and to assign nurses fewer patients.

In a statement, HCA, which owns Mission Hospital, said its highest priority was to protect workers and that the unions were “exploiting the situation in an attempt to gain publicity and organize new dues-paying members.”

In addition to staging protests and strikes, unions have defended workers who are speaking up against their employers. Some unions have sued hospitals, including one lawsuit against Riverside by the SEIU. Similar cases have been dismissed in court, and HCA called the Riverside suit a publicity stunt.

Industry executives say the unions are unfairly blaming hospitals for the horrors of the pandemic. While some had difficulty providing protective equipment early on, hospitals have done their best to follow government guidelines and to protect workers, said Chip Kahn, president of the Federation of American Hospitals, which represents for-profit hospitals.

Kahn said the unions were leveraging the crisis to achieve their agenda of organizing workers. “They’ll push whatever pressure points they can to try to force their way into hospitals, because that’s what they do.”

About 17 percent of nurses and 12 percent of other U.S. health care workers are covered by a union, according to an analysis of government data, and rates of union coverage have remained largely unchanged during the pandemic. The share of hospital workers with union representation has declined from above 22 percent in 1983 to below 15 percent in 2018, reflecting a decades-long decline in organized labor.

Some unions, including the outspoken National Nurses, have often seemed to occupy the fringes of the labor movement. For years it was better known for advocating proposals like Medicare for All, which would replace private insurance with government-run health care, and for enthusiastically backing Sen. Bernie Sanders (I-Vermont), for president.

The pandemic and the union’s decision to endorse President Joe Biden after Sanders left the race last year have tempered that reputation. Mission nurses said that politics was not part of the allure of National Nurses United. “Of all the unions we could’ve gone to, they had the best track record,” Fischer said.

The Biden presidency may give the unions an opportunity to flex their newfound muscle. Mary Kay Henry, international president of the SEIU, was among the labor leaders who met virtually with Biden last year.

“In my 40 years of organizing health care workers, I have never experienced a time when people are more willing to take risks and join together to take collective action,” Henry said. “That’s a sea change.”