Travellers arriving at Heathrow and Gatwick from west Africa are to be screened for symptoms of Ebola, Downing Street announced on Thursday night after a day of confusion over the government’s response to the virus that has claimed more than 3,800 lives.

People travelling from the worst-affected countries – Liberia, Sierra Leone and Guinea – will face a questionnaire about their recent travel history, who they have been in contact with and their onward travel arrangements.

Medical staff will be deployed to check some travellers’ body temperature to ascertain if they have fever, one of the early symptoms of the illness. Rail passengers arriving in Kent and London on the Eurostar from Paris and Brussels will also be screened.

Cases have already been reported in Spain and the US, where Thomas Eric Duncan died on Thursday after flying in from Liberia with the disease.

Washington has announced that travellers from the worst-hit countries will have their temperatures taken on arrival at five major airports in New York, Washington, Chicago and Atlanta.

The UK border measures will be introduced “in the coming days”, Downing Street said, and the announcement came despite the British defence secretary, Michael Fallon, saying earlier on Thursday that airport screening was not in line with World Health Organisation advice that screening for fevers or temperature is better conducted in the exit country.

The chief medical officer, Professor Dame Sally Davies, cited “concern about the growing number of cases” of the illness and recommended border checks to ensure “potential cases arriving in the UK are identified as quickly as possible”.

Public Health England staff will work alongside border officers. No 10 was unable to say whether the system would catch travellers from west Africa who had transferred planes in other cities.

The apparent U-turn comes before a war game-style test of Britain’s ability to cope with an outbreak being planned by the Department of Health this weekend. Doctors, the ambulance service, local authorities and the police will take part in the real-time simulation of Ebola cases at two or more hospitals to be selected in the north and south of England.

No 10 said: “Advice from the chief medical officer today is that enhanced screening arrangements at the UK’s main ports of entry for people travelling from the affected regions – Liberia, Sierra Leone and Guinea – will offer an additional level of protection to the UK.

“These measures will help to improve our ability to detect and isolate Ebola cases. However, it is important to stress that given the nature of this disease, no system could offer 100% protection from non-symptomatic cases.”

The Foreign Office was last night investigating reports that a Briton had died of suspected Ebola in Macedonia. Tests were being carried out but the man’s colleague said he had not been in any country known to have Ebola outbreaks. A social services centre in Paris which was sealed off after four children recently arrived from Guinea showed symptoms of the illness, was later reopened after the French authorities said it was a false alarm.

Pressure for airport screening grew yesterday when Keith Vaz, chairman of the Commons home affairs select committee, which scrutinises border controls, called for tests “to ensure that this deadly disease cannot take more lives”. Andy Burnham, the shadow health secretary, also urged the government to consider passenger screening “without delay”.

Davies said: “Rapid access to healthcare services by someone infected with Ebola is not only important for their health but also key to reducing the risk of transmission to others. These measures could include a further UK-based package of measures to identify and assess the health status of passengers arriving from the affected countries and to ensure that those individuals know what to do should they be taken ill whilst in the UK.”

Experts say airport screening may have limited effect. David Heymann, professor of infectious diseases at the London School of Hygiene and Tropical Medicine, who is also chairman of Public Health England, said there was a danger of creating a false sense of security .

“It is not a failsafe method mainly because people cross [borders] while they are still in the incubation period and you don’t know they are infected,” he said.

“The most important response is better detection and rapid response. Borders cannot stop infectious diseases spreading. In Hong Kong and Singapore they set up thermal scanners during the Sars epidemic but I don’t think they identified more than one case that way.”

Professor David Mabey, another physician specialising in infectious diseases at the London School of Hygiene & Tropical Medicine, warned passengers will lie about their travel history to avoid the inconvenience and so would be “a waste of time”.

“If last week your aunt died of Ebola but you feel fine, are you going to be honest when you get to the airport and risk being detained?” he said.

Professor George Griffin, chairman of the advisory committee on dangerous pathogens, said screening just for body temperature was ineffectual and would have missed the case of the US death.

Experts also moved to play down fears of a major UK outbreak. Peter Piot, a Belgian microbiologist who is part of the World Health Organisation’s Ebola science group, said: “I’m not concerned about an outbreak in western Europe, in the UK, like we are seeing in west Africa.”

Heymann said British preparedness to cope with Ebola cases was “superb”.

“The government and the NHS has access to all clinicians so messages can get out to all of them at once and that means it is much easier to achieve uniformity than in private systems,” he said.

He added that the public health authorities in the UK has successfully stopped two outbreaks of the deadly Middle East respiratory syndrome, a virus which, unlike Ebola, can be transmitted through the air.