At least six Transportation Security Administration officers have tested positive for the new coronavirus and dozens were in self-quarantine Monday as the disease takes an increasing toll on an agency critical to the safety of US aviation.

TSA said it was providing safety training to employees and operations were running smoothly. It stood by its decision to not provide officers with respirators as their union requested last week.

Union leaders said they were still concerned, even as a major drop in traffic at the nation’s airports seemed to reduce the potential for exposure. Officers screen 2 million passengers around the country on a typical day.

Joe Shuker, a vice president for the union representing workers in the region that includes Philadelphia and Washington, said he was surprised the government hadn’t shut down air traffic.

“Our guys can’t stay six feet away from anybody, we’re patting people down,” Shuker said. ’We’re putting people at risk for no reason.”

TSA over the weekend announced the positive test of an officer at Orlando International Airport who had last been at work March 10. The officer was being treated and all employees who came into contact with the person over the previous two weeks were in self-quarantine at home.

There was an earlier positive test by an officer at the Fort Lauderdale-Hollywood International Airport and four at the airport in San Jose, California.

The TSA did not disclose the total number of employees in isolation because of the exposure but the American Federation of Government Employees, which represents the nearly 46,000 officers, said about 40 workers at just the San Jose airport were told to self-quarantine.

Around the globe, airline bookings are plummeting and cancellations soaring as governments restrict travel and people fear being enclosed in an airplane for several hours during a pandemic that has sickened more than 180,000 people and killed more than 7,100.

TSA said checkpoints remain open though some lanes may be closed. Shuker said the Philadelphia airport was unusually quiet. “There are enough people because nobody is flying,” he said. “This place should be packed right now on a Monday,”

AFGE sent a letter last week to the TSA director asking that he provide respirators because surgical masks they were given are insufficient for officers who “are uniquely susceptible to this outbreak.” The request was denied.

The agency said in response to The Associated Press that neither the CDC nor the Occupational Safety and Health Administration recommends respirators for the officers and says the equipment should be reserved for workers in the riskiest situations such as medical personnel.

“TSA follows OSHA and CDC guidance related to personnel protection,” it said in a written statement.

The agency said it was requiring officers to wear nitrile gloves while checking people and baggage to add an extra layer of protection and instructing them not to reuse swabs used in screening, among other measures.

Gary Holdsworth, a union vice president for the local in Northern California, said there has not been any mass sickout in response to the outbreak despite the increasing stress of potential exposure. “You don’t want to panic and you don’t want to be paranoid, but when you are in a spot where you are seeing the public every day you have no idea,” he said.

Greg Biel, a union regional vice president in Portland, Oregon, said workers were frustrated about what they see as a poor job planning for the outbreak but weren’t letting that interfere with their work. “From what I can see, everybody is coming to work and doing the job they were brought on board to do,” he said.