Several jail staffers took notice when an inmate arrived at a federal detention center in Miami last week wearing a mask.
Word spread rapidly inside the FDC Miami that the man had flu-like symptoms, two workers said, triggering fears that the inmate was infected with the coronavirus.
"A lot of staffers are in an uproar because they don't know if they're going to get exposed," an employee told NBC News at the time.
It turned out that the inmate had a bacterial infection, a Bureau of Prisons official said, not coronavirus. But concern about the potential spread of COVID-19 inside a detention facility has only grown since then as the number of confirmed cases has exploded across the country.
An outbreak of the deadly virus inside the walls of a U.S. prison or jail is now a question of when, not if, according to health experts. And interviews with several jail staffers, prisoner advocates and former correctional medical personnel revealed deep concerns over the potential for the illness to wreak havoc behind bars.
"We're in a very perilous stage right now," said Dr. Homer Venters, the former chief medical officer of the New York City jail system. "It's just a matter of time before we see cases inside jails and prisons."
Venters regularly visits jails and prisons across the country as an expert consultant on health services in correctional settings. He said it's common to see facilities lacking the kind of basic germ-fighting tools necessary to help prevent the spread of an illness like the coronavirus.
"Let's say there are three sinks for 40 people," said Venters, who is the president of Community Oriented Correctional Health Systems, a nonprofit that works to improve health care behind bars.
"Rarely do I ever see most of them working, plus soap and paper towels. Some of the most basic elements of infection control that we take for granted, like your ability to wash your hands and dry them, remain out of reach for many people in detention."
The U.S. has roughly 5,000 adult detention facilities — a mix of jails, which house inmates awaiting trial or serving short sentences, and prisons, where people convicted of serious crimes go to serve time. No cases have yet been reported in any of the facilities.
But the environments, with inmates packed together in often grimy spaces with limited ventilation, provide a prime breeding ground for the spread of infectious diseases, experts say.
Jails are seen as being especially vulnerable, given the constant flow of prisoners in and out. Several jail systems have announced coronavirus countermeasures, such as stepped-up cleaning and ramped-up medical screening of new arrivals.
But more dramatic measures, such as restricting inmate visitation, had yet to be put in place on a grand scale until late Thursday, when several states announced that they were suspending visitation until further notice.
Prisoner advocates worry that the virus has already made its way inside the walls of the nation's detention facilities.
"My fear is it will be similar to the assisted living facility in Washington state, where no one's going to know until it becomes a very serious matter somewhere," said Maria Morris, a senior staff attorney with the American Civil Liberties Union's National Prison Project.
Morris said the combination of staffers moving in and out of prisons and the already unsanitary conditions inside many of them increase the likelihood of serious coronavirus outbreaks.
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"Once it gets in, if there's not a well-thought-out plan to address it, it seems very likely that it'll wreak havoc on facilities quite quickly," she said.
Countries hard hit by the coronavirus have already experienced major problems inside their prisons. Deadly riots broke out in facilities across Italy amid efforts to contain the virus. In China, where it originated, at least 500 prisoners have been infected. And Iran took the extraordinary step of temporarily releasing more than 50,000 prisoners in hope of slowing the spread of the virus.
Joe Rojas, the Southeast regional vice president for the Council of Prison Locals, the union that represents federal prison workers, said he fears the potential for riots to erupt.
"When there's fear among inmates without a plan for containment, you can have a riot," Rojas said.
He said that many federal prisons are also dealing with staffing shortages in their medical departments and that a lack of guidance from the Bureau of Prisons has fueled workers' fears.
"People are freaking out about it, and we don't have the resources," Rojas said.
A spokeswoman for the Bureau of Prisons said: "Out of an abundance of caution, the BOP provided guidance to health-care professionals throughout the system and has a screening tool in place for use in the event an inmate or staff member is exposed or symptomatic. The BOP has an internal web-based system for reporting infectious diseases and outbreaks, allowing access to health care and correctional professionals system-wide."
Federal prisons are not stocking COVID-19 test kits, the spokeswoman said, but medical personnel working with local health authorities can facilitate inmate testing.
"Every BOP facility has contingency plans in place to address a large range of concerns, to include infectious diseases, and is fully equipped to implement these plans as necessary," the spokeswoman added.
Unlike prisons, the majority of local and county jails lack in-house medical staffs, experts say, making it far more difficult to combat a fast-spreading illness like the coronavirus.
"There are jails where the sheriff's deputies are handing out medications and making medical decisions for the individuals," said Sheriff Dave Mahoney, who operates a 1,000-bed facility in Dane County, Wisconsin.
Mahoney, who is the incoming president of the National Sheriffs' Association, said he and his counterparts around the country are having ongoing discussions about a range of potential countermeasures — from instituting video-only visitation to increasing alternatives to incarceration for lesser crimes.
"With the flu, we could at least warn people to get the flu shot at the beginning of the year and reduce the volume of the virus, and even if they got the flu, they could mitigate the effects by getting a Tamiflu shot," Mahoney said. "Well, those things don't exist for the coronavirus."
In January, the Henderson County Detention Center in central Kentucky had a trial run of sorts for dealing with a coronavirus outbreak when more than 200 inmates came down with a mysterious stomach bug.
The jail moved quickly to contain the spread of the illness, moving the sick inmates to a special wing where the recirculated air goes nowhere else and ramping up cleaning the old-fashioned way.
"Bleach and water," said head jailer Amy Brady, who runs the facility. "We had inmates running in shifts."
The symptoms disappeared after 12 hours. The same month, an area doctor who treats inmates at the detention center offered sage advice: stock up on specialized masks amid reports of a worsening virus in China.
The masks, known as N95 respirators, are now in short supply across the country.
"We have 250 of them," Brady said. "I feel pretty good. But like anything else with the jails, there's always the likelihood that it's going to spread."