Media playback is unsupported on your device Media caption Passengers from certain countries arriving at five US airports will have their temperature taken

Travellers from Ebola-affected countries will face increased security scrutiny at five major US airports.

Passengers from Liberia, Sierra Leone and Guinea will have their temperatures taken and have to answer questions.

The new measures at O'Hare in Chicago, JFK and Newark in the New York area, Washington's Dulles, and Atlanta's airport will begin in the coming days.

The Ebola outbreak has already killed more than 3,000 people and infected more than 7,200, mostly in West Africa.

The increase in passenger testing comes after the first person diagnosed with Ebola on US soil died in Dallas on Wednesday.

Thomas Duncan travelled to the US from Liberia, and was only diagnosed with the disease once he arrived in Texas.

A police officer who visited Mr Duncan's home is now reported to have Ebola-like symptoms and has been taken to hospital as a precaution.

Frisco Mayor Maher Maso described the risk as "minimal", but officials were taking "an abundance of caution"

Test results were expected back within about 48 hours, Mr Maso said.

'Most likely malaria'

Customs and Border Protection (CBP) will dispatch staff to these five airports, which account for 90% of travellers to the US. As many as 160 people enter the US from those countries each day.

Media playback is unsupported on your device Media caption Barack Obama: "Our military is building an infrastructure that does not exist"

Travellers will be given a questionnaire, and if they answer yes to any questions or are running a fever, a representative of the Centers for Disease Control and Prevention (CDC) will intervene and provide a public health assessment.

Factsheets will be distributed to travellers with information on symptoms of Ebola and instructions to call a doctor if they become ill within three weeks.

"We expect to see some patients with fever and that will cause some obvious and understandable concern," said CDC director Dr Tom Frieden. But those cases will most likely be malaria, which is widespread in West Africa, he said.

If a patient does display a fever, he or she may be handed over to local health workers for further oversight.

The changes are currently set to begin at JFK on Saturday and the other four airports some time next week.

"We're always looking for ways we can better protect Americans," Dr Frieden added. But, given the ongoing nature of the Ebola outbreak in West Africa, "we can't get the risk to zero in this country".

Earlier, President Barack Obama said the new security measures would "give us the ability to isolate, evaluate and monitor travellers as needed, and we'll be able to collect any contact information that's necessary".

"If we don't follow protocols and procedures that are put in place, then we're putting folks in our communities at risk," he added. "We don't have a lot of margin for error."

Image copyright AP Image caption Mr Duncan, shown here at a 2011 wedding in Ghana

Sickness in Spain

Secretary of Homeland Security Jeh Johnson described the measures as "an additional layer of protection to help ensure the risk of Ebola in the United States is minimised."

More than 3,400 people have already died in West Africa, and on Monday, Liberian national Thomas Eric Duncan became the first person to die of the disease in the US. He was also the first person diagnosed with the disease outside of Africa.

The first case of contagion outside that continent was also confirmed in Spain on Monday, where a nurse who treated an Ebola victim in Madrid contracted the virus herself.

Passengers leaving affected countries already have their temperatures checked, but people do not become infectious until they display symptoms.

Mr Duncan was screened for symptoms when he left Liberia but appeared healthy. He did not develop symptoms of Ebola until four days later, when he was in the US.

Forty-eight people who came into contact with him, not counting the quarantined Dallas County deputy, are being monitored by health officials.

The CDC chief has ruled out banning flights to the US from the affected countries, arguing the isolation would only worsen the outbreak within Africa and would deny those countries crucial aid.