United States experts unsure about viability of plans for Ebola screening for airline passengers

US President Barack Obama's pledge to boost screening for Ebola-infected airline passengers will mean devising a way to check thousands of flights arriving daily at US airports for those who are ill but symptom-free.

While United and Delta airlines are the only US-based operators serving Africa, heightened Ebola vigilance would require a broad net, covering travellers on other non-stop flights from the continent and those who connect via European carriers in hubs such as London and Paris. Fliers at risk would then need to be scrutinised for any history of exposure to the disease.

"It's probably good politics at this point to say we need better screening and more screening," said Richard Bloom, director of terrorism, intelligence and security at Embry-Riddle Aeronautical University in Arizona.

"Unless someone is blatantly symptomatic - having diarrhoea, bleeding from body orifices and vomiting - it's very difficult to figure out who might pose more of a risk than others," he said.

With Ebola spreading in West Africa and the first case diagnosed in the US last month, Obama promised more rigorous passenger scrutiny on Monday without giving details.

Officials were not considering a ban on air travellers from West Africa, White House press secretary Josh Earnest said.