(CNN) -- New measures at U.S. airports to screen for people possibly carrying the Ebola virus will include taking passengers' temperatures and handing them questionnaires, according to a federal official and a second person briefed on an announcement the federal government plans to make Wednesday.
The enhanced methods, focused on people coming from West African nations hit by the Ebola crisis, will begin soon at New York's JFK airport and then expand to four other major international airports: Newark, Chicago, Washington Dulles and Atlanta.
Among the countries considered to be in the so-called Ebola zone are Guinea, Sierra Leone, Liberia and Nigeria.
The new measures at U.S. airports come a day after Dr. Thomas Frieden, the director of the CDC, told reporters that devising travel guidelines was in the works but nothing had yet been finalized enough to announce.
The Ebola virus can spread through contact with bodily fluids -- blood, sweat, feces, vomit, semen and saliva -- and only by someone who is showing symptoms, according to the CDC.
People with Ebola may not be symptomatic for up to 21 days.
Symptoms generally occur abruptly eight to 10 days after infection, though that period can range from two to 21 days, health officials say.
Air travelers must keep in mind that Ebola is not transmitted through the air, said Dr. Marty Cetron, director of the CDC's Division of Global Migration and Quarantine.
"There needs to be direct contact frequently with body fluids or blood," he stressed.