The two American aid workers getting treated in Georgia for Ebola are isolated in a special ward that some staffers at Emory University Hospital call “Noah’s Ark.” But they’re not the first Americans ever quarantined for Ebola on US soil.

A decade ago—according to a little-noticed article in the journal Emerging Infectious Diseases—a virologist at the US Army Medical Research Institute of Infectious Diseases in Bethesda, Maryland was working in the facility’s Biosafety Level 4 lab, famous for its depiction in Richard Preston’s 1994 book The Hot Zone. This still-anonymous researcher was working with mice infected with a mouse-adapted variant of Ebola Zaire. After the scientist injected four of them with an immune serum, the fifth mouse kicked. The needle bucked and pierced the virologist’s glove and skin. She followed procedure: She squeezed the wound to force out the infected blood, decontaminated her full-body protective suit in the lab’s chemical shower, poured a liter of sterile water on her hand, and scrubbed with povidone-iodine for 10 minutes.

Nobody really thought the virologist was infected, but everyone wanted to be sure. So her bosses at USAMRIID sent her to “the Slammer,” more formally known as the Medical Containment Suite (and nicknamed for the sound the doors made when they shut behind you). The Slammer, part of USAMRIID’s facility at Ft. Detrick, was for 30 years the only patient isolation unit in the US. Built in the early 1970s, it had two 180-square-foot rooms so that scientists working on the worst of the worst diseases could lock themselves and their potential infections inside, keeping outbreaks from ever breaking out. The suite saw about 20 patients over its lifespan, all researchers who were thought to have been exposed to monsters like Lassa, Machupo, and Junin. None ever actually became ill. The Ebola-exposed virologist was the first person to use the suite in 15 years; she spent 21 days there. She was fine.

Even though it never housed an actual sick person, the Slammer became the blueprint for a half dozen similar facilities around the country—negative pressure air, HEPA-filtered ventilation and single-pass air to keep airborne evils inside the room. Medical staff dress in full-body “moon suits,” walk through doors with airtight gaskets and decontaminate themselves and supplies three ways, with an autoclave, an ultraviolet light box and a disinfectant dunk tank.

After bioterrorism scares in the wake of 9/11 and SARS concerns in 2003, other facilities started thinking about building their own slammers. USAMRIID knew it might need to treat its own researchers as they handled deadly and weird diseases, but hospitals around the country had tumbled to a truth beyond that: The kinds of diseases their own patients might get exposed to were changing—for the worse. So the hospitals had to change, too.

It’s built like a concrete box. We want to keep our germs inside.The Care and Isolation Unit in Montana, opened in 2005 by the National Institutes of Health to serve lab workers at Rocky Mountain Laboratories, hasn’t yet served an infectious disease patient, only a handful with tuberculosis or contagious bacterial infections. The rooms look like everyday hospital rooms—white, sterile, a TV and window for entertainment. That’s because St. Patrick Hospital retrofitted three of its ICU rooms to make the unit. In fact, it still serves as ICU space when the wing is overrun. “It’s great to have the rooms at the ICU because we can quickly move infectious patients and have an experienced nursing staff right there,” says George Risi, the unit’s infectious disease adviser. “But one of the big aspects with cases such as Ebola or SARS is overcoming health care worker reluctance.”

When the Missoula unit opened, Risi created a training program for doctors and nurses that explains how to put on protective gear and follow isolation procedures. The program uses simulations with mannequins filled with fluorescent liquids that represent infectious body fluids, and the team runs through the procedures twice a year. As part of the program, Risi highlights a 2009 case in Colorado and how doctors handled a woman who returned from Uganda with the hemorrhagic fever Marburg, a cousin of Ebola. “They couldn’t establish the diagnosis at first and took care of her in standard fashion. She lived,” he explains. “No one was infected because the staff at this community-based hospital was aggressive about following guidelines. Details make all the difference.”

That’s why hospital staff volunteers at Nebraska Medical Center run twice yearly drills with decontamination at their hospital’s 10-bed biocontainment unit. It’s the country’s largest, opened in 2005 with $1 million in federal and state funding. “It’s built like a concrete box,” says Angela Hewlett, the unit’s associate medical director. “We want to keep our germs inside.” But like Missoula, Nebraska hasn’t seen a single infectious disease patient. Sometimes they use it as overflow for the emergency room.

In fact, newer isolation wards tend to be designed to accommodate those multiple uses—and to be nicer places to get locked into. According to Bruce Ribner, the infectious disease specialist at Emory leading the care team watching over the two American aid workers, Noah’s Ark—built in 2002—at least has glass windows so patients inside can see out, and communicate. In 2010, USAMRIID decommissioned the Slammer; NIH opened a seven-bed Special Clinical Studies Unit at the Clinical Research Center in Bethesda to replace it. Its four patient rooms (two doubles and a single) are way more comfortable than the Slammer and designed for ongoing research as well as isolation. In recent trials, volunteers agreed to be infected with H1N1 or seasonal flu strains for experimenters to analyze how long it takes for flu symptoms to appear, when the virus becomes contagious, how long symptoms last and how the body responds.

“We decided at the outset that we weren’t going to have a unit waiting for some occupational exposure, which is very infrequent,” said Richard Davey, deputy clinical director of NIH’s Division of Clinical Research. “We wanted a fully functional unit for other reasons to serve NIH’s mission of clinical and lab research.”

Built with SARS as the worst-case scenario in mind, the Bethesda unit has only served a patient with a drug-resistant bacterial illness. “It can handle the highest level of respiratory virus, but Ebola isn’t even spread that way,” Davey added.

This kind of design is likely the blueprint for future facilities, with Biosafety Level 4 labs under construction at Kansas State University and Boston University. The nature of outbreaks is changing, so the hospitals and labs must change as well—building expensive medical suites that researchers hope they’ll never have to use.