A man who flew from Liberia to Dallas has become the first Ebola case to be diagnosed within the U.S., the CDC reported Tuesday, and he is currently in isolation at Dallas's Texas Health Presbyterian Hospital.
Americans have been warned not to travel to Liberia, Guinea, or Sierra Leone, but they obviously can—and do.
So how are countries keeping suspected Ebola patients (well, most of them, anyway) contained within their borders?
People are screened for elevated temperatures before they're allowed to board planes departing from the countries where Ebola is raging. Fever is one of the earliest symptoms of Ebola, but people can be infected for between two and 21 days without showing signs of illness.
The Washington Post's Todd Frankel described having an infrared thermometer gun pointed at his head in the Freetown, Sierra Leone airport, along with hundreds of other passengers. In some countries, individuals whose temperatures seem high later undergo a blood test for the virus.
But these temperature checks aren't always effective. In the Dallas case, the man left Liberia on September 19, had his temperature checked at the airport, and arrived in America on September 20. He only developed symptoms on the 24th, however, and he was isolated four days later. Patients are only contagious when they're symptomatic, so there's no risk the people on the flight with the man caught Ebola. There is, however, a four-day window in which he might have infected others in the U.S.