New York's JFK airport began strict new health screenings Saturday for travelers arriving from Ebola-hit West African nations, amid growing US fears about importing the deadly virus.

John F. Kennedy International was the first of five airports to introduce the tougher measures, meant to provide a layer of protection in a nation jittery over fresh cases of the illness after the first patient diagnosed on US soil with Ebola died Wednesday.

A spokeswoman for the Centers for Disease Control and Prevention (CDC) told AFP that Customs and Border Protection agents had met planes arriving at JFK with passengers to be checked.

Four other airports -- Newark, Chicago's O'Hare, Washington Dulles and Hartsfield-Jackson Atlanta International -- are due to start the checks next week.

Together, the airports account for 94 percent of all travelers coming into the United States from Guinea, Liberia and Sierra Leone, the countries hardest-hit by the epidemic that has killed more than 4,000 people.

Passengers arriving at any of the five airports from those countries will have their temperatures taken, be assessed for signs of illness and answer questions about their health and exposure history.

Some could be barred from traveling further or referred to nearby hospitals if necessary.

"If the traveler has a fever or other symptoms or has been exposed to Ebola, Customs and Border Protection will refer that traveler to the Centers for Disease Control for a public health assessment," CBP chief Gil Kerlikowske told reporters at JFK airport, one of the busiest in the United States.

He said passengers suspected of serious illness could be issued "Do Not Board" notifications.

The travel ban could be applied to "individuals considered infected with a highly contagious disease... and (who) should be prevented from traveling on international aircraft," he said.

Although the health checks provide an enhanced layer of protection, the CDC cautioned that screenings are not airtight.

The screenings were not expected to clog arrival terminals, with only about 150 passengers per day set to be examined at all ports of entry, CDC Director Tom Frieden told CNN.

Around half of arrivals from the three West African countries pass though JFK airport.

More airports to follow

The scaled-up measures were put in place after the death on Wednesday of Thomas Eric Duncan, the first person diagnosed with Ebola outside Africa. The Liberian man died in a Texas hospital after being given an experimental drug.

His case sparked panic about the possible spread of the deadly virus in the United States, though President Barack Obama said the chances of a US Ebola outbreak were "extraordinarily low."

Ebola is transmitted by close contact with the bodily fluids of an infected person.

The incubation period for the disease is two to 21 days, during which carriers may not present Ebola symptoms such as fever, vomiting and diarrhea.

Five Americans have returned from West Africa for treatment of Ebola infection, including three Christian missionaries who got sick in Liberia and have since recovered.

A sixth US citizen, Patrick Sawyer, who held dual Liberian-American nationality, died of Ebola in July after traveling by plane from Liberia to Nigeria.