The Obama administration on Wednesday said authorities will soon begin temperature checks and health surveys of travelers from Liberia, Sierra Leone and Guinea arriving at five U.S. airports in an effort to halt the spread of Ebola to the U.S.

What have officials been doing to prevent Ebola-infected people from flying?

In the most-affected countries, Liberia, Sierra Leone and Guinea, local authorities are screening all outbound fliers with questionnaires, visual assessments and temperature readings, The Wall Street Journal reports.

Over the past two months, authorities there have screened about 36,000 fliers, according to the U.S. Centers for Disease Control and Prevention. Just 77 of those fliers showed symptoms of Ebola, but none are believed to have the disease.

Airlines have been told to watch for telltale symptoms among passengers in-flight. In the U.S., Customs and Border Protection workers have been tasked with observing travelers for signs of illness.

What are the new screening measures?

After their passports are reviewed during immigration checks, passengers arriving from Liberia, Guinea and Sierra Leone to five U.S. airports will be pulled aside to a separate screening area where Customs and Border Protection staff will question them about their health and exposure to Ebola, take their temperature with an infrared thermometer and collect their contact information in the U.S.

The screenings will begin on Saturday at John F. Kennedy International in New York, and then next week start at O’Hare International in Chicago, Hartsfield-Jackson International in Atlanta, Washington Dulles International near Washington, D.C., and Newark Liberty International in Newark, N.J. Authorities said more airports may follow.

What happens if someone has a fever or reports contact with someone with Ebola?

An on-site officer from the Centers for Disease Control and Prevention would further assess the individual and determine whether he should be sent to a hospital or to local public-health officials. If a traveler reports recent contact with someone with Ebola, the CDC said that at a minimum, it would ensure the traveler’s temperature is taken for 21 days after the last exposure. The incubation period for Ebola is between two and 21 days.

How many people will be affected by these screenings?

The White House said that the five U.S. airports receive 94% of the roughly 150 passengers from the three affected countries that arrive in the U.S. each day.

How could this affect other U.S. travelers?

Travelers who haven’t visited one of the three affected countries should notice little or no change. The travelers subject to additional screening represent a fraction of 1% of the people who travel annually to the U.S. The additional screening will also take place in a separate area, meaning it shouldn’t hold up immigration lines.

What risk remains for passengers?

Air travelers are at little risk from contracting Ebola simply by sharing a flight with an infected person, according to health officials. The disease can’t be transmitted through airborne particles and only people who are exhibiting symptoms are contagious. Symptoms include a fever, which should preclude a person from boarding a plane in the most-affected countries under screening protocols there.