The virus has killed almost half the people infected in the three African nations. Amid calls for better protection, U.S. agents at John F. Kennedy International Airport yesterday added screening of passengers who began their trips in one of the three nations. In total, 91 people were pulled aside for special questioning. None had a fever, and five were asked more questions by a health worker, Frieden said. Other airports will be adding the procedures in coming days.

Airport Checks

Of the 275,000 international passengers daily, about 150 -- or less than 0.1% -- come from at-risk regions in Africa. The three African nations conduct their own screening of outbound passengers.

The new U.S. airport checks started three days after the first U.S. death from Ebola. The patient, Thomas Eric Duncan, arrived in Dallas from Liberia on Sept. 20 and didn’t show signs of the disease until Sept. 24. He died at Texas Health Presbyterian Hospital, where the health-care worker was an employee.

With fears of possibly more cases to come, some analysts say it’s time to block people from outbreak countries from entering the U.S., while preserving ways for relief workers to get in or out.

‘Inhibit’ Flows

“Whatever we can do to inhibit the flow of human traffic, the more the better,” said James Wilson, co-founder and chief scientist of Ascel Bio, a Larchmont, New York-based disease forecasting and surveillance company. “I’d suggest it’s time to have a real blunt discussion with our State Department.”

Other analysts say travel restraints could be counterproductive, putting more stress on the affected countries, undercutting their economies and risking the failure of their governments.

Without a decision by the Geneva-based World Health Organizations to limit travel, a U.S. travel ban would both “violate international law and be unethical,” said Lawrence Gostin, a Georgetown University professor who has written on the health-related travel issues. “It would cause enormous human problems, and would make the epidemic harder to control.”

The current system is “imperfect,” but better than a ban -- for now, said Ronald Bayer, a co-director of the Center for the History and Ethics of Public Health at Columbia University.

Isolation, Hysteria

“The problem with a total travel ban is that it feeds a sense of isolation and hysteria,” Bayer said. “It would be disruptive and dangerous.”

Worried that avian influenza could become a worldwide pandemic, the administration of President George W. Bush did extensive studies to see if travel bans could help stop an outbreak. The results indicated that travel bans wouldn’t work and might interfere with the movement of crucial supplies and health personnel.

“These things are not very effective and there are lots of unintended consequences,” said Michael Leavitt, who was Bush’s secretary of Health and Human Services.

The WHO ruled out travel restrictions based on an assessment that showed the disease isn’t spread through the air, a decision that led the International Air Transport Association in Geneva to oppose a ban on flights to the region.

“Aviation is a lifeline for these nations, and a provider for these markets,” said Chris Goater, a spokesman for the airline group. “There is a lot of disquiet among the flying public.”

Still, the current efforts aren’t nearly enough for many lawmakers.

“If we were really treating this as a public health issue why would we not immediately stop these flights,” Representative Joe Barton, a Texas Republican, said at a hearing with federal health and border officials in Dallas last week. “You’re almost guaranteeing mathematically we’re going to miss some people” with Ebola, he said.

--With assistance from John Lauerman in Boston and Drew Armstrong in New York.

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