It seems so obvious: To keep Ebola out of the United States, simply keep anyone who has the deadly disease from getting in.
Some prominent Obama administration critics have made that argument this week, calling for a travel ban into the U.S. from the West African nations of Liberia, Sierra Leone, and Guinea, where more than 3,400 have died of the virus and thousands more are infected. There's a growing social media chorus calling for a ban, too. (Related: As Ebola's Spread Continues, Key Questions and Answers)
By cutting off travel from the Ebola zone, the thinking goes, someone like Thomas Duncan—the Liberian diagnosed with Ebola in Dallas last week and died Wednesday morning in a Dallas hospital—would never have made it into the United States. Ebola is not detectable (or contagious) until the patient develops symptoms such as fever and vomiting, so Duncan's illness could not have been diagnosed until after he arrived in the U.S.
The U.S. government does appear ready to increase screening of air passengers arriving in the United States from several West African nations by taking their temperatures, a federal official told CNN on Wednesday. And yet the Obama administration has steadfastly rejected the idea of an outright ban on travel to and from West Africa.
Thomas Frieden, director of the U.S. Centers for Disease Control and Prevention, has been asked repeatedly about a travel ban in near-daily briefings with the press over the past week. Each time, he has insisted it won't work.
Frieden, who is heading the government's Ebola response, has gone as far as to say that a travel ban could hurt Americans in the long run, by limiting the ability of relief workers and supplies to get into West Africa's Ebola zone.
"Until the disease is controlled in Africa, we can't get the disease to zero here," Frieden said at a Tuesday news conference. (Related: "Every Newly Emerging Disease Like Ebola Begins With a Mystery.")
Public health experts generally back the administration's actions, and most oppose a travel ban, at least for the moment. But they say the issue is more nuanced than Frieden has made it out to be. A travel ban would have kept Duncan from bringing Ebola to the U.S., they say, and could keep out some future infected travelers.
"It is a question, I think, on which people can honestly disagree," said Stephen S. Morse, professor of epidemiology at Columbia University's Mailman School of Public Health. "There are good arguments to be made on both sides. It's partly a philosophical choice."
Politics and Perception
Six African countries have already banned or suspended flights from Liberia, Guinea, and Sierra Leone, and others have instituted other travel restrictions. (Related: "Doctors and Nurses Risk Everything to Fight Ebola in West Africa.")
And since late August, the U.S. State Department has urged Americans to avoid all non-essential travel to Liberia, Sierra Leone, and Guinea.
But Congressman Alan Grayson, a Florida Democrat, wants the U.S government to go further. Grayson said he would propose legislation calling for a ban if the administration continues to avoid one.
"It will prevent infected travelers in whom Ebola is asymptomatic and undetectable from traveling to the United States and then exposing Americans to the disease after they become symptomatic," he said by e-mail.
It takes anywhere from 2 to 21 days for someone who has been exposed to the Ebola virus to show symptoms. People who are not symptomatic are not contagious, and Duncan did not have symptoms while he was traveling and so could not pass the virus on to fellow passengers. No one who came into contact with Duncan has yet become ill, though several family members and contacts are under observation until the 21 days have elapsed.
A number of high-profile Republican politicians, including Texas Senator Ted Cruz and Kentucky Senator Rand Paul, have said that more needs to be done to keep Ebola victims from arriving on U.S. soil. But they've stopped short of demanding a full ban.
Wendy Parmet, director of the Program on Health Policy and Law at Northeastern University School of Law, in Boston, said that travel bans are appealing because they make people feel safe. But she argued that safety could be an illusion.
"It gives us the false assurance that we can ignore the problems that are happening in Africa," she said. "At the end of the day, we can't. And our own safety depends on our getting it right there, not on building the walls."
Would a Ban Matter?
Many public health experts who oppose the travel ban argue that it's simply not practical. That includes Columbia University's Morse, who describes himself as a "fence-sitter" on the issue but doesn't support a travel ban right now because people with financial means can travel to an intermediate country before entering the United States. West Africa's many porous borders make such travel even easier, he said.
It wouldn't make sense to ban people who fly out of Senegal—where, like the United States, there has been only one case of Ebola, Morse said. But if one person with Ebola made it there, others could, too.
A ban could also encourage people to lie about where they have been, Morse said: "One of the real concerns is that if you outlaw [travel], it will discourage people from coming forth with the truth."
Frieden, for his part, has focused his opposition to a travel ban on the hardship it would present for fighting the epidemic in Africa.
"If we do something that impedes our ability to stop the outbreak in West Africa, it could spread further there," he said Tuesday.
On Sunday, Frieden also cited the example of Senegal, which has restricted flights from the affected countries. The restrictions delayed the arrival of investigators looking for people who had come into contact with the country's one Ebola patient.
Plus, international volunteers who go into West Africa to help treat Ebola patients need to know that they can get back out, Frieden said.
At SIM, an international mission that has led Ebola treatment centers and seen two of its American missionaries recover from the virus, travel restrictions might make volunteers think twice, said George Salloum, who leads the agency's Ebola crisis response team.
"Anything you do to restrict movement of people back and forth or keeping them from getting back to work, it could have an impact on the flow of people willing to serve overseas," he said.
Screening at Airports—and Beyond
Those on both sides of the travel ban debate appear to support aggressive airport screening, to ensure that sick people won't be able to get on a plane and potentially infect fellow passengers.
President Obama on Monday announced plans to step up airport screening in the United States and in West Africa, evaluating travelers for signs of illness, better informing airport personnel on how to spot Ebola, and handing out fact sheets to incoming passengers from affected countries.
He did not reveal specifics about what he would change and did not mention a travel ban.
Frieden said Tuesday that he would announce more details in a few days. Among measures being considered, he said, are temperature checks and questionnaires given to passengers arriving in the United States. On Wednesday morning, CNN reported that temperature checks will begin this weekend or next week on passengers whose travel itineraries include the affected West African nations.
Frieden said that 77 people have been blocked from leaving the affected countries since this summer, when officials began questioning travelers and screening their temperatures at airports in Guinea, Liberia, and Sierra Leone. None of them tested positive for Ebola, he said, adding that they most likely had malaria, a mosquito-borne disease that shares early symptoms with Ebola.
A temperature check could have stopped Patrick Sawyer, a Liberian-born American citizen who flew from Liberia to Nigeria in late July while sick with Ebola, from spreading the disease.
Sawyer directly or indirectly infected 20 people in Nigeria, eight of whom died, as did Sawyer himself. It's unclear whether he knew he had Ebola when he left Liberia. A travel ban likely would not have stopped Sawyer from entering because he was a U.S. citizen, though an effective temperature scan would have.
Still, airport screening is hardly foolproof. Duncan may have lied when answering questions about whether he had been exposed to anyone with Ebola. Or he may not have realized that helping a pregnant neighbor to the hospital in Liberia exposed him to the virus, Frieden said.
Beyond airports, hospitals are an important second line of defense against Ebola, said Jill Holdsworth, an infection control practitioner at Inova Mount Vernon Hospital in Alexandria, Virginia.
Duncan's symptoms were missed as Ebola the first time he went to Texas Presbyterian Hospital in Dallas, although he apparently indicated that he had recently arrived from Liberia. Several hospital workers and the ambulance drivers who took Duncan back to Texas Presbyterian two days later may have been exposed because of that mistake.
"As soon as a patient walks in, if they present with a fever, you should ask them about recent travel history," said Holdsworth, who is also a spokesperson for the 15,000-member Association for Professionals in Infection Control and Epidemiology. "If they say yes, they immediately get taken to a room until we can figure out what's going on. That's what every hospital has to be doing."