The Trump administration says millions of workers in fields the administration deems "critical" who were exposed to COVID-19 should return to their jobs as long as they wear masks, despite evidence that people without symptoms can spread the novel coronavirus.

The advice spans 16 industries designated by the White House in a memo dated Monday. Those include doctors, nurses and paramedics, but also hundreds of jobs in other fields, such as cafeteria workers, people who process financial transactions, food delivery drivers and defense contractors, according to Vice President Mike Pence, who leads the White House's task force on the coronavirus. 

"Those workers, even if they've been exposed to someone with coronavirus, as long as they don't have symptoms, would be able to return to work immediately, wear a mask for two weeks, but otherwise return to the important roles that they play in all of our communities," Pence said Monday in remarks at the Federal Emergency Management Agency headquarters in Washington. 

The guidance, which is not binding but is designed to guide state and local governments, comes as President Donald Trump has said he is eager to "reopen the economy" by Easter, on April 12, to stanch losses in the stock market and avoid spiking unemployment.

Katie McKeogh, a spokesperson for the Health and Human Services Department, pointed to the administration's March 16 Coronavirus Guidelines for America, which states"if you work in a critical infrastructure industry, as defined by the Department of Homeland Security, such as healthcare services and pharmaceutical and food supply, you have a special responsibility to maintain your normal work schedule." 

CDC recommends that asymptomatic people with a risk of developing COVID-19 self-isolate. But last week it began making an exception for workers in these "critical infrastructure positions." Employers can require people with those sorts of jobs to report to work, the CDC says, but the agency recommends managers take employees' temperatures before their shifts.

A spokesperson for the vice president's office confirmed the guidelines were in effect. 

The recommendations from the White House come as some workplaces have seen walkouts over fears of COVID-19 exposure, including sanitation workers in Pennsylvania, shipyard workers in Maine, agriculture employees in Georgia, and bus drivers in Alabama.

Trump has defied the calls of epidemiologists and government public health officials who say his Easter timeline is too optimistic in part because the United States was slow to begin testing people for the virus and it's unclear who has it. Shelter-at-home orders by state governors are meant to give hospitals more time to acquire supplies and clear bed space.

People without symptoms can spread the coronavirus that causes COVID-19, but that sort of "asymptomatic transmission" does't cause most cases, the CDC says. However, some global data shows that carriers of the virus who don't show symptoms are a driver of transmission.

It's hard to determine the extent of the virus' spread in the United States and the role of asymptomatic transmission because of limited testing. Nine weeks after the first U.S. case, about 367,710 people have been tested, according to the COVID Tracking Project.

"Without knowing who has been exposed, these recommendations seem dangerous," said Durland Fish, professor emeritus of epidemiology at the Yale School of Medicine.

Labor leaders opposed

Labor unions have opposed the relaxing of public health guidelines as a way of getting people back to work, preferring economic stimulus.

"Peopl's lives are at stake," said Lee Saunders, president of the American Federation of State, County and Municipal Employees, in a call with reporters Tuesday. "We've got an administration talking about well, this may be a problem but we’ve got to get back to work because of the economic fallout that may exist in the country. I think that's irresponsible."

CDC already relaxed workplace safety standards for health care workers. Hospitals in crisis can require doctors and nurseswho were exposed to COVID-19 to return to work as long as they wear a mask and consult with staff clinicians, according to guidance updated last week. 

The CDC recommends health care providers who have been exposed to the virus stop treating patients and only begin treating them again after a negative test, or after symptoms have gone away. But the agency also provides a loophole for hospitals and nursing homes facing a shortage of manpower if they "determine that the recommended approaches cannot be followed"

Requiring workers to report to their jobs after exposure could put more people at risk, unions say.

"New guidelines from the Centers for Disease Control and Prevention that effectively encourage hospitals to require health care staff to return to work while infected with the COVID-19 virus threaten to put countless number of dedicated health care workers at risk and further spread the virus," said Bonnie Castillo, the executive director of National Nurses United.

Health care workers remain at risk of infection, and quarantine, because of a continuing shortage of safety gear, including surgical masks and the N95 masks that can filter for airborne viruses, according to nurses unions.

The CDC's recommendation coincides with a carveout in a bill to expand paid leave for emergencies related to COVID-19 Congress cleared last week that expressly omitted health care workers. 

Trade associations representing hospitals and nursing homes have supported the CDC's relaxed recommendations, saying a crush of COVID-19 patients could require all hands on deck. But they also say that the real impediment to getting workers back on the job is a shortage of diagnostic tests. 

Pence indicated Sunday that health care workers can get tested quickly, even if they don't have symptoms. But that is not true in nursing homes across the country, according to David Gifford, chief medical officer of American Health Care Association/The National Center for Assisted Living, an association of thousands of nursing homes and assisted living facilities. 

Workers are asking for tests and "getting declined," Gifford said. "We support the CDC guidance, but the lack of testing and not making our workforce a priority is making matters worse."

Jared Rosenberg, who supervises paramedics for the police department in Greenburgh, N.Y., said the lack of available testing is leading to a shortage of staff, hampering his department's ability to respond to COVID-19-related emergencies, which he says now comprise about 20 percent of its emergency calls. 

"We cannot afford to have between 10 percent and 15 percent of our workforce unable to report to work for almost two weeks because they don’t know if they’ve been exposed," he said. 

Epidemiologists want the CDC to issue stricter guidance on when employers can require workers to return.

Peter Hotez, dean of the National School of Tropical Medicine at the Baylor College of Medicine, said the CDC should issue clear criteria depending on the nature of the exposure to the virus and should also take steps to test workers three or four days after they've been exposed, when the virus would begin showing up on a test. 

But tests are scarce, and state health departments report that some results can take several days.

"I think this is a prelude to a White House proposal that mitigation measures be relaxed in favor of restoring the economy," said Yale's Fish. "This is bad science, but science does not always prevail in political decisions."