Twenty-six-year-old nurse Nina Pham is the first person to catch Ebola from an infected human on U.S. soil. Pham is now in isolation at Texas Health Presbyterian Hospital in Dallas and the U.S. Centers for Disease Control and Prevention (CDC) has launched an investigation into safety practices at the hospital where she works and is being cared for.

The source of Pham's infection is clear: She cared for Thomas Duncan after he entered the isolation ward at the hospital on September 30. (Duncan caught the virus in Liberia but did not become sick until after he traveled to Dallas.) What is unclear is how Pham became infected even though she was wearing protective gear. 

The news, which broke on Sunday morning, substantially changes the approach to dealing with Ebola in the clinical setting, CDC Director Thomas Frieden said in a press briefing Monday. "If this one individual was infected within the isolation unit, then it is possible that other individuals could have been infected as well. We're doing an in-depth review and investigation." The agency has since sent an additional team from the CDC and from Emory University to Dallas to help the hospital beef up its infection control

Health officials reported on Tuesday that they are now closely monitoring 76 hospital workers at the hospital who cared for Duncan during his time in isolation. This is in addition to the 48 individuals they were watching who had close contact with the Liberian native while he was sick but before he was hospitalized.  

See Scientific American's In-Depth Report, Ebola: What You Need to Know.

"The care of Ebola can be done safely, but it is hard," Frieden said Sunday morning at another of the now-daily news conferences about Ebola that CDC is holding. "It requires meticulous and scrupulous attention to infection control, and even a single inadvertent innocent slip can result in contamination," he said. "The protocols work," but at some point in the care of Duncan, "there was a breach in protocol, and that breach of protocol resulted in this [new] infection."

10 steps to safety?
Hospital policies on health care worker precautions are based on government recommendations. According to the CDC (pdf), workers going into isolation units should, at a minimum, wear gloves; goggles or a face shield; a gown; and a mask or respirator. And all of those caring for Duncan were fully clothed in such protective gear, Texas Commissioner of Health David Lakey said in a call with reporters Monday. (To be clear, such garb, which is technically referred to as personal protective equipment, or PPE, is not the same as the full hazmat suits seen in some images from Ebola cleanup programs in Africa.)

But simply covering up is not enough to prevent spread of the virus. In addition to ensuring that no skin is exposed, health care workers must exercise extreme caution while with the isolated patient—to avoid needle pricks and other accidental routes of contamination. And perhaps the most challenging link in the chain is the exiting procedure. After leaving the isolation area a healthcare worker must be fastidious in properly removing each potentially contaminated item safely. "Health care workers need to be meticulous," says Jeff Duchin, a professor of infectious diseases at the University of Washington School of Medicine and chief of communicable disease and epidemiology for Public Health—Seattle and King County, who spoke with Scientific American about infection control. "The potential to expose yourself is real." (CDC video clips from a field training demonstration show how cumbersome the suiting-up process is and how difficult proper equipment removal can be.)

The CDC has two prescribed methods (pdf) for safely removing protective equipment. Each tactic involves at least 10 distinct steps—from removing gowns from the inside out (starting with neck and shoulders) to which ties on a mask to grab first (the bottom)—and admonitions to wash hands immediately if they accidentally come into contact with the exterior of any piece of gear. "Doing this right 100 percent of the time does require very intensive training, follow-up [and] monitoring," Frieden noted.

Duchin agrees: "The art of taking off the gear is difficult to master." Pham received her critical-care nursing certificate this August after having completed her nursing degree four years ago, according to reporting by NBC. There are no credentials required for individuals or institutions who deal with isolation treatment, Lakey noted. Critical-care nurses specialize in treating those with life-threatening conditions, although those afflictions are not always infectious and more often are likely those with cancer or accident victims. And it is unclear what specific isolation protocol training those caring for Duncan received.

Invasive procedures performed on Duncan might have also increased healthcare workers' risk. For example, he received kidney dialysis—in which blood is filtered out of the body for cleaning by a machine—as well as respiratory intubation—in which a breathing apparatus is placed down the throat while a separate suction device removes saliva and other liquids. These invasive procedures are rare in Ebola cases, in part because, as Duchin notes, "most managing of Ebola patients has been in field hospitals in Africa where the ability to use those treatments is not high." Such procedures might open healthcare workers up to additional exposure by increasing contact with virus-laden body fluids. Even on the front lines of the Ebola battle in Monrovia, Doctors Without Borders (MSF) temporarily stopped giving patients potentially life-saving intravenous fluids to reduce the risk of healthcare worker infection, The New York Times recently reported.

Health officials still don't know what went wrong in Pham's case. "If we knew that there was a specific incident, such as a needle stick," Frieden said, "we could narrow down the health care workers at risk to those who had that specific exposure. Since we don't know, we have to cast the net more widely."

Real-time improvements
The CDC team is intently watching healthcare workers now caring for Pham and is requiring individual monitors—a type of buddy system—to observe staff as they enter, work in, and exit isolation areas to ensure all of the steps are followed.

After about 24 hours of monitoring, the CDC said by Monday morning it had already helped the Dallas hospital institute improvements to their infection control protocols. "We're not going to wait for the final results of the investigation," Frieden said Monday. "Each time we identify a process or training or equipment or protocol that can be improved there we are improving it right there on the site." In a call Tuesday Frieden noted that, in addition to training by Emory University Hospital nurses who cared for Ebola patients there, they are focused on assessing equipment and how it is handled both before and after the healthcare worker contacts an infected patient. The team is also considering spraying down gear to kill any virus on it before removal, an approach that is common in Ebola treatment centers in Africa.

Neither the CDC nor Texas Health Presbyterian Hospital would provide additional details to what procedures have changed, although the hospital acknowledged its willingness to accept CDC guidance. "We're working at all levels with the CDC to coordinate all care-related issues," said Barclay Berdan, CEO of Texas Health Resources, which owns the Dallas hospital, in a town hall meeting with staff Monday.

Although it might seem counterintuitive, extra protective gear is not necessarily better, Frieden noted in a press conference Monday. In hopes of staying safe healthcare workers "may put on additional sets of gloves or additional coverings," he said. And the cleaning company that sanitized the Dallas apartment where Duncan had been staying noted that their workers wore three layers of gloves. But, Frieden said, "that may actually end up, paradoxically, making things less rather than more safe because it may be so difficult to remove those layers that it inadvertently increases risk," he explained. More is also not always wise in terms of staff and procedures, Frieden noted. Keeping both to the minimum is important for reducing transmission risk; having fewer staff on the case, for example, means that "they can become more familiar and more systematic in how they put on and take off protective equipment," he said Tuesday.

Lessons and directives
Pres. Barak Obama directed the CDC on Sunday to move quickly in conducting its investigation at the Dallas hospital—and requested that hospitals nationwide step up their familiarity with safety protocols for handling Ebola patients.

Should another patient be diagnosed with the virus, Frieden noted, he or she might now be taken to a center specially equipped to handle such infectious cases, such as Emory University Hospital or Nebraska Medical Center, where patients diagnosed in Africa were treated and released earlier this year. Such centralizing "does make a lot of sense from a strategic perspective," Duchin says. But, he notes, "regardless of whether or not you're going to designate centers for Ebola patients, they're not going to show up there. They're going to show up at their local emergency room." And for that all hospitals need to be prepared not just to diagnose patients in a timely fashion but also to quickly and safely isolate them. Even if patients are eventually transferred to the best-equipped facilities, they might need to spend a day or two at the local hospital being stabilized and prepared for transport, Duchin says. And that will require local healthcare workers to follow exacting protocols, which nursing organizations say they could use more training.

As Frieden pointed out Monday, "we've already cared for other patients with Ebola in this country without infections," alluding to the Americans diagnosed in Africa but treated and released here. But if anything, Duchin says, through these first cases, "we're learning that we don't have a lot of experience with Ebola patients."

Pham is the second person to have caught the virus outside of Africa. The first was the Spanish nurse's assistant Teresa Romero who was diagnosed earlier this month after caring for an infected Spanish missionary patient who died. She reports accidentally brushing her face with a contaminated glove, which might have transmitted the virus to her.

Pham was reported to be in good condition as of Tuesday evening. She brought herself into the emergency room over the weekend after noticing a low-grade fever on Friday. Such self-reporting was requested of all workers who cared for Duncan while he was in isolation.

Infectious disease experts have determined only one possible at-risk contact from before Pham went into isolation. And, as Frieden noted Monday, that was very early on in her illness when she would have been less likely to transmit the virus. Once a patient becomes sicker—as Duncan, the index patient was on his admission into isolation—the quantities of virus in that person's bodily fluids rise, making them more infectious.

Frieden said he "would unfortunately not be surprised if we did see additional cases in the healthcare workers who also provided care to the index patient." But, he noted, for those outside of the direct contact circles the CDC is actively monitoring in Dallas, unless you travel to west Africa, there is currently no risk of others in the U.S. contracting the disease.