PROVIDENCE, R.I. -- Vilified, threatened with violence and in some cases suffering from burnout, dozens of state and local public health leaders around the U.S. have resigned or have been fired amid the coronavirus outbreak, a testament to how politically combustible masks, lockdowns and infection data have become.

One of the latest departures came Sunday, when California's public health director, Dr. Sonia Angell, was ousted following a technical glitch that caused a delay in reporting hundreds of thousands of virus test results -- information used to make decisions about reopening businesses and schools.

Last week, New York City's health commissioner was replaced after months of friction with the Police Department and City Hall.

A review by the Kaiser Health News service and The Associated Press finds at least 49 state and local public health leaders have resigned, retired or been fired since April across 23 states. The list has grown by more than 20 people since the AP and KHN started keeping track in June.

Dr. Tom Frieden, former director of the Centers for Disease Control and Prevention, called the numbers stunning. He said they reflect burnout, as well as attacks on public health experts and institutions from the highest levels of government, including from President Donald Trump, who has sidelined the CDC during the pandemic.

"The overall tone toward public health in the U.S. is so hostile that it has kind of emboldened people to make these attacks," Frieden said.

The last few months have been "frustrating and tiring and disheartening" for public health officials, said former West Virginia Public Health Commissioner Dr. Cathy Slemp, who was forced to resign by Republican Gov. Jim Justice in June.

"You care about community, and you're committed to the work you do and societal role that you're given. You feel a duty to serve, and yet it's really hard in the current environment," Slemp said in an interview Monday.

The departures come at a time when public health expertise is needed more than ever, said Lori Tremmel Freeman, CEO of the National Association of County and City Health Officials.

"We're moving at breakneck speed here to stop a pandemic, and you can't afford to hit the pause button and say, `We're going to change the leadership around here and we'll get back to you after we hire somebody,"' Freeman said.

As of late Monday, confirmed infections in the United States stood at over 5 million, with deaths topping 163,000, the highest in the world, according to the count kept by Johns Hopkins University. The confirmed number of coronavirus cases in the world topped 20 million with about 734,000 deaths.

Many of the firings and resignations have to do with conflicts over mask orders or social distancing shutdowns, Freeman said. Despite the scientific evidence, many politicians and others have argued that such measures are not needed, no matter what health experts tell them.

"It's not a health divide; it's a political divide," Freeman said.

Some health officials said they were stepping down for family reasons, and some left for jobs at other agencies, such as the CDC. Some, like Angell, were ousted because of what higher-ups said was poor leadership or a failure to do their job.

Others have complained that they were overworked, underpaid, unappreciated or thrust into a pressure-cooker environment.

"To me, a lot of the divisiveness and the stress and the resignations that are happening right and left are the consequence of the lack of a real national response plan," said Dr. Matt Willis, health officer for Marin County in Northern California. "And we're all left scrambling at the local and state level to extract resources and improvise solutions ... in a fractured health care system, in an under-resourced public health system."

Public health leaders from Dr. Anthony Fauci down to officials in small communities have reported death threats and intimidation. Some have seen their home addresses published or been the subject of sexist attacks on social media. Fauci has said his wife and daughters have received threats.

In Ohio, the state's health director, Dr. Amy Acton, resigned in June after months of pressure during which Republican lawmakers tried to strip her of her authority and armed protesters showed up at her house.

It was on Acton's advice that GOP Gov. Mike DeWine became the first governor to shut down schools statewide. Acton also called off the state's presidential primary in March just hours before polls were to open, angering those who saw it as an overreaction.

The executive director of Las Animas-Huerfano Counties District Health Department in Colorado found her car vandalized twice, and a group called Colorado Counties for Freedom ran a radio ad demanding that her authority be reduced. Kim Gonzales has remained on the job.

In West Virginia, the governor forced Slemp's resignation over what he said were discrepancies in the data. Slemp said the department's work had been hurt by outdated technology like fax machines and slow computer networks. Tom Inglesby, director of the Center for Health Security at Johns Hopkins, said the issue amounted to a clerical error easily fixed.

Inglesby said it was deeply concerning that public health officials who told "uncomfortable truths" to political leaders had been removed.

"That's terrible for the national response because what we need for getting through this, first of all, is the truth. We need data, and we need people to interpret the data and help political leaders make good judgments," Inglesby said.

Since 2010, spending on state public health departments has dropped 16% per capita, and the amount devoted to local health departments has fallen 18%, according to a KHN and AP analysis. At least 38,000 state and local public health jobs have disappeared since the 2008 recession, leaving a skeletal workforce for what was once viewed as one of the world's top public health systems.

Another sudden departure came Monday along the Texas border. Dr. Jose Vazquez, the Starr County health authority, resigned after a proposal to increase his pay from $500 to $10,000 a month was rejected by county commissioners.

Starr County Judge Eloy Vera said Vazquez had been working 60 hours per week in the county, one of the poorest in the U.S. and recently one of those hit hardest by the virus.

"He felt it was an insult," Vera said.

In Oklahoma, both the state health commissioner and state epidemiologist have been replaced since the outbreak began in March.

In rural Colorado, Emily Brown was fired in late May as director of the Rio Grande County Public Health Department after clashing with county commissioners over reopening recommendations. The person who replaced her resigned July 9.

Brown said she knows many public health department leaders who are considering resigning or retiring because of the strain.

The months of nonstop and often unappreciated work are prompting many public health workers to leave, said Theresa Anselmo of the Colorado Association of Local Public Health Officials.

"It will certainly slow down the pandemic response and become less co-ordinated," she said. "Who's going to want to take on this career if you're confronted with the kinds of political issues that are coming up?"

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Weber reported from St. Louis. Associated Press writers Paul Weber, Sean Murphy and Janie Har, and KHN writer Anna Maria Barry-Jester contributed reporting.

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Weber is a reporter with Kaiser Health News. This story is a collaboration between The Associated Press and KHN, which is a non-profit news service covering health issues. It is an editorially independent program of KFF (Kaiser Family Foundation) that is not affiliated with Kaiser Permanente.