Public health officials are reaching out to as many as a hundred people who may have come into contact with the first Ebola patient to be diagnosed in the U.S., quizzing them about their interactions with the man, who has been identified as Thomas Eric Duncan.

Any who are found to have come within three feet of him are considered to have been in close contact and will be monitored over the next three weeks to ensure they don't develop symptoms of the virus, said Thomas Frieden, director of the U.S. Centers for Disease Control and Prevention, at a Thursday news conference.

See graphic:
 Ebola: Tracking the Outbreak

The Ebola virus has sickened more than 7,100 people in West Africa this year, killing more than 3,300 of them, according to the World Health Organization.

Social media is buzzing this week with concerns about the disease, the U.S. government's handling of it, and the likelihood of its spread. "My angst and frustration about ebola situation is there was no strategy in place," tweeted self-described marketing specialist @musicloverchick on Thursday. "The US never thinks it will happen here."

Some public health officials also voiced frustrations on Thursday, specifically with regard to how Duncan's case was handled. The man had told an intake nurse at a Dallas hospital that he'd recently been to Liberia, but the information reportedly wasn't shared with the medical team diagnosing his case and he was initially sent home.

"Unfortunately, connections weren't made related to travel history and symptoms," said Frieden, addressing the communication breakdown in Duncan's case. He added that a questionnaire given to travelers as they leave Liberia asks whether they had any exposure to Ebola patients and that Duncan did not report any.

Nurses Speak Out

A union representing 185,000 nurses nationwide, meanwhile, said its membership does not feel confident that they are adequately prepared to deal with the disease.

"I'm sure there is a plan somewhere; unfortunately, it's not being shared with those who are actually taking care of the patients," Karen Higgins, co-president of National Nurses United and an intensive care unit nurse in Boston, said in an interview from a nurses conference in Massachusetts. "We're in a room full of nurses, and there's nobody who feels like 'I know what to do if I ended up with a patient.'"

In a poll of 400 National Nurses United members released Wednesday, 60 percent said their hospital is not prepared for the Ebola virus, and more than 80 percent said their hospital had not educated them about Ebola or communicated any policy regarding potential patients infected with the virus.

Nearly one-third of the nurses said their hospitals lacked sufficient supplies of face shields and fluid-resistant gowns needed to protect them against the virus.

The union, which staged a "die-in" Monday on the Las Vegas strip to call attention to their Ebola concerns, blamed a lack of information and proper systems—rather than human error—for the decision last week to let Duncan leave the hospital when he first turned up complaining of fever and abdominal pain and mentioned his recent trip to Liberia. He was sent home but was readmitted on Sunday, much sicker.

It's not clear why the information about his recent travels did not raise a red flag in the emergency department, and why he was not suspected of having Ebola.

In a prepared statement in response to questions about the nurses' concerns, the American Hospital Association released a statement from Ken Anderson, the chief operating officer for the organization's Health Research and Educational Trust.

"We strongly recommend that hospitals follow CDC guidance in identifying potential Ebola patients," the statement said. "While in the Dallas case the hospital has acknowledged that it had a regrettable lapse in communication, the AHA is redoubling our efforts to make sure hospitals are aware of the latest CDC guidance, including checklists and screening criteria."

Frieden described the missed opportunity to catch Duncan's disease earlier as a "teachable moment," and said the CDC is redoubling its efforts to provide clear and useful information to hospitals about the Ebola risk.

"Essentially, any hospital in the country can safely take care of a patient with Ebola," he said, by providing a private room and bathroom, and by "rigorous, meticulous training" of staff. But Frieden acknowledged that the CDC is still working through the challenge of how to safely dispose of medical waste from Ebola patients.

Reassurances on Containment

Despite the Dallas incident and the possibility of other Ebola patients arriving from overseas or the disease spreading in the United States, there is virtually no chance of an out-of-control outbreak in the U.S., said Joel Selanikio, a former outbreak investigator with the CDC and now CEO of a mobile data collection company called Magpi.

"[It] is like hearing that there's a forest fire in Sierra Leone, and thinking that if someone brings a match back from there we'll have it here," he said. "We've got a fire department and they don't."

The Texas Department of State Health Services announced Thursday that it has placed four of Duncan's family members under quarantine in their Dallas home where he had been staying, with a police guard standing at the door.

The family members' temperatures are monitored twice a day to make sure none of them develop a fever, said David Lakey, the state health department commissioner, adding that he wasn't confident such monitoring would happen without the quarantine, which he referred to as a "control order."

A cleaning service was hired Thursday to clear the home of some of Duncan's belongings, including his clothes and bedding, which have been placed in garbage bags in the home, Lakey said. Lakey said he does not anticipate having to place any of Duncan's other contacts under control order.

Duncan left Liberia's capital of Monrovia on September 19. His temperature was checked at the airport and reported to be a perfectly normal 97.3 degrees, Frieden said. People with Ebola are contagious only after they have begun showing symptoms, so Duncan was not contagious during his travels, which reportedly included flights through Brussels and Washington, D.C., en route to Dallas.

Frieden said the exit form given to travelers as they leave Liberia asks whether they had any exposure to Ebola. Duncan did not report any, though published reports say he helped his landlord in Monrovia take his sick daughter to the hospital, where she died. "The reality is that individuals often don't know what their exposures have been and not all individuals fully disclose what their exposure has been," Frieden said.

Duncan began feeling ill on the September 25 and went to the emergency room at Texas Health Presbyterian Hospital Dallas, complaining of fever and abdominal pain. He apparently told the intake nurse that he had recently traveled to Liberia.

But he was given an antibiotic—which is ineffective against a viral illness—and sent home.

Between the 24th when he began feeling ill and the 28th when he was taken to the same hospital with severe symptoms, he came into contact with as many as a hundred people, Texas health officials said Thursday.

Duncan remains in serious condition at Texas Health Presbyterian.

Frieden said it wouldn't make sense to ban all travel from West Africa in an attempt to prevent future travelers from bringing Ebola the U.S. A travel ban would make it harder to fight the disease in West Africa, allowing it to spread further, which would put more people both there and here at risk, he said.

"The best way to protect ourselves is not to try to seal ourselves off, but to provide the kind of services that are needed so the disease is contained there and to identify any that may come out," he said. "The only way to get to zero risk is to stop it there."