Amid growing panic about the Ebola outbreak in West Africa, Republicans in Congress are shifting away from calling for a blanket travel ban from countries affected by the disease, and moving instead toward wanting to limit visas for people from those countries.

While banning visas may seem like a watered-down travel ban, it would actually be more successful at targeting people trying to enter the U.S. from countries affected by the Ebola outbreak than an outright ban.

Sen. Marco Rubio proposed a bill Monday that would temporarily ban the U.S. from issuing new visas to citizens of Liberia, Guinea, and Sierra Leone. The bill would ban the issuance of any new visas to those countries, except for people who have traveled to the U.S. to help combat the disease. Rubio will introduce his bill when the Senate returns in November, heralding what could be a big fight of the lame-duck session: How should the U.S. respond to fears about the Ebola outbreak?

"Since March 1, 2014, over 6,000 visas have been issued to nationals of these countries. Foreign health workers coming to the United States to be trained should be exempted, provided they pass screening efforts," Rubio wrote last week. "However, until we have a better handle on the problem, we need to prevent mass travel from the countries most affected."

Rubio joins an ever-growing bloc of lawmakers pushing for travel restrictions for people coming from West Africa. So far, 72 House members and 15 senators support a blanket travel ban from countries battling Ebola.

But as Kaveh Waddell wrote last week, it's hard to say how the U.S. government would go about imposing such a ban. U.S. airport hubs are already screening passengers for fever and other Ebola symptoms, and health experts have said that an outright ban would not be feasible. That's because people traveling from West Africa to North America often take circuitous, multi-leg routes, making it more difficult to track their travel.

That's where the visa ban would come into play. "Banning new U.S. visas for Liberian, Sierra Leonean, or Guinean nationals would make it hard for those people to evade detection, because it would restrict their entry to the U.S. no matter where their journey begins," The Wall Street Journal reports.

There are also economic considerations to take into account. President Obama's administration has insisted until now that a travel ban is unnecessary, in part because of the limited spread of the disease to the U.S. If the White House suddenly said that a travel ban is necessary, that could send shock waves through the stock market and create public panic.

Perhaps for that reason, the State Department has shot down the visa ban idea as well as an outright travel ban.

"There are no plans to suspend visa operations at this time. We can't control this epidemic through the visa process," State Department spokesperson Marie Harf said on Monday. "If you end legitimate means of travel out of West Africa, it could result in people's smuggling and illicit ways of people traveling, which would just make it harder for us to track sick people, to prevent them from crossing borders."

If you are a citizen of Liberia, Guinea, or Sierra Leone, you can't come to the U.S. unless you have some type of visa. Depending on the type of visa, Liberian and Guinean travelers can stay in the U.S. anywhere from one month to 10 years. Immigrants from Sierra Leone can stay in the U.S. on a visa up to five years.

The incubation period for Ebola, by comparison, is roughly 21 days. During that period, someone with the disease would not necessarily show detectable symptoms—in a blood test or with a fever. The upside is that, someone who is not showing symptoms of the disease cannot spread the disease. While no Ebola patients have been proven to infect others by coughing or sneezing, The New York Times reports that patients "emit copious amounts of highly infectious vomit, blood, and diarrhea."

A visa ban isn't close to a perfect solution. A hypothetical: If an American citizen unknowingly contracted Ebola while visiting Liberia, then traveled to the U.S. without exhibiting symptoms, she wouldn't need a visa to get back across the border before her symptoms began to manifest. But if you're a Liberian citizen who has been living in Europe, with absolutely no contact with the virus, you could be stopped by the visa ban if you try to travel to the U.S.

At this point, all-out panic is unwarranted. On Monday, Dallas County officials cleared the 43 people who have been monitored for Ebola over the past 21 days. Those people had all come in contact with Thomas Eric Duncan, the Liberian man who died in a Dallas hospital on Oct. 8 after contracting the disease before coming to the U.S. Two nurses who treated Duncan have been infected by the virus, and five other people who had contact with Duncan are still being monitored for the disease.

The U.S. government is in a tight spot: Ban visas, and it could alienate African allies. Don't ban visas, and take the gamble that a future Typhoid Mary will be detected before spreading the disease to the U.S. Damned if they do, damned if they don't.

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