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. 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. More via Nat Geo.