There are reasons the U.S. hasn't enacted a travel ban on countries where Ebola has broken out: It wouldn't work and could actually make things worse, health officials say.

Still, that's done little to quell the calls for a ban.

On Friday, Texas Gov. Rick Perry became the latest politician to call for one for anyone seeking to enter the United States from affected areas of West Africa. Two days earlier, House Speaker John Boehner called on President Barack Obama to issue a temporary travel ban on Ebola-afflicted countries "as doubts about the security of our air travel grow." His request came after a second U.S. nurse was diagnosed with Ebola after treating a Liberian man who died of the disease in Dallas, and after she flew from Dallas to Cleveland and back.

A Washington Post-ABC News Poll said that 67 percent of Americans support restricting entry to the U.S. to travelers who have been in Ebola-affected countries.

Other countries — most recently including Jamaica, Guyana, Trinidad and Tobago, Colombia, and St.Lucia — have already taken steps to ban travelers from Liberia, Guinea and Sierra Leone or restrict entry until after a 21-day quarantine. Nigeria, Senegal and Democratic Republic of Congo are also on some of the banned lists.

By the numbers: Ebola in perspective

While the Centers for Disease Control and Prevention says it remains open to all effective options that will make Americans safer, "we can't have anything happening right now that slows our ability to stop the epidemic," CDC spokesman Tom Skinner said.

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"When some commercial flights stop going into those countries, our people are delayed going in, our people are delayed going out," Skinner said. "When we stop commercial flights in and out of the country, it does not enhance our ability to stop the epidemic."

But maybe those types of logistics are best left to military logistics experts, said David Dausey, a doctor and the dean of the School of Health Professions and Public Health at Mercyhurst University in Erie, Pa. The Ebola crisis now demands a mobilization akin to a war, he said. "We should be handling this with the same sense of urgency."

There is no need to entirely close the borders of the affected countries, he said, but their airports should be temporarily closed to commercial flights, and foreign military should act fast to fill the gap for aid efforts with the same speed as if they were responding to a natural disaster.

No Ebola epidemic in US without 'mutation': CDC

While the U.S. has pledged aid and military help, White House Press Secretary Josh Earnest on Thursday made clear the president is not considering a travel ban. "Currently, when individuals do travel from West Africa to the United States they are screened prior to departure in West Africa. They are screened again once they enter this country, and they are subjected to heightened screening if they have traveled in these three West African countries in the last three weeks or so," Earnest said, referring to the five airports with extra screenings that see 94 percent of travelers from those countries.

"Now, if we were to put in place a travel ban or a visa ban, it would provide a direct incentive for individuals seeking to travel to the United States to go underground and to seek to evade this screening and to not be candid about their travel history in order to enter the country," he said. "And that means it would be much harder for us to keep tabs on these individuals and make sure that they get the screening that's needed to protect them and to protect, more importantly, the American public."

Many health experts agree that a ban isn’t necessary.

"You're not preventing the movement of the population anyway," said Harvard epidemologist John Brownstein. "Many of these countries have very porous borders."

And there's no evidence that travel bans have any lasting effect, he said. Brownstein co-authored a study that found that the airport closures in the eastern U.S. after 9/11 did delay the onset of flu that year, but only by two weeks.

"Ultimately these pathogens find their way around the globe," said Brownstein.

A ban on travel could also hurt the local economies in Africa.

Nigeria saw a big decline in air travel over the summer. In August, ticket sales from the United States to Nigeria were down 31 percent over the same time a year earlier, according to information for all airlines collected by the Airlines Reporting Corp. financial group. By September, when Nigeria's situation had improved, the decline was only 20 percent. The country hopes to get a final Ebola clearance from the World Health Organization within days.

Tourism to the three worst-afflicted countries is limited even in healthy times — they represent less than 0.5 percent of all international travel to Africa, said Sandra Carvao, spokeswoman for the United Nations World Tourism Organization.

Even so, the economic impact of a travel ban "would be tremendous," said Robert Brunner, a vice president for Arik Air, the largest airline in West Africa. "These are countries that are fragile to start with, and it wouldn't take much to tip them when things get harder than they are. …

"And if you're banning air travel, would there also be a call to ban ship travel? Any port of call is banned as well?" Brunner asked, referring to potential ways around a travel ban.

If you're going to start isolating people who don't even show symptoms, he said, "Where does it stop?"