Media playback is unsupported on your device Media caption Actors played the parts of Ebola patients, as Jane Dreaper reports

The UK should expect a "handful" of Ebola cases in the coming months, the chief medical officer has said.

Defending a screening programme due to start at key airports and stations, Dame Sally Davies said it was a "blunt instrument" but would save lives.

She rejected criticism in a leaked email circulated to doctors that the screening was a "political gesture".

The UK held exercises earlier to test its response to an outbreak, as the US began screening some arriving there.

Ebola has killed more than 4,000 people worldwide, and a UN expert has said the world will live with it "forever" unless global action stops the virus.

'Vitally important'

Dame Sally, England's chief medical officer and chief medical adviser to the UK government, said any cases in Britain would be "spill-over" from West Africa.

She said the screening was "unlikely" to pick up many cases, "if any". But she stressed the "great advantage" would be that people would be alerted to what symptoms to look for and what to do if they fell ill.

This would reduce their chances of dying and of spreading the virus to others, she said.

Image copyright Department of Health Image caption Medics in the exercise wore full protective suits, which can be used to stop the spread of the Ebola virus

Passenger screening, to be introduced at Heathrow and Gatwick airports and Eurostar terminals next week, will include the assessment of passengers' travel history and a "possible medical assessment".

The Department of Health said further details would be announced next week before the measures came into effect.

Similar measures are being taken in the US, with screening under way at New York's JFK airport and checks at some other airports due to start in the coming days.

In an email seen by the BBC, a senior consultant involved in the programme said he believed the UK screening was "purely a political gesture, unlikely to provide public health benefits".

BBC political correspondent Carole Walker said she had spoken to another consultant, also involved in the programme, who had questioned whether someone wanting to enter the UK would be honest if he or she had come into contact with Ebola.

The consultant also raised concerns about why health workers involved in screening were not being given protective clothing - saying this must mean they were either not expected to find anyone with Ebola, or they were expected to stop infected people without proper protection.

Responding criticism from doctors, Dame Sally said: "At this time, this is the right thing to do."

Media playback is unsupported on your device Media caption Chief Medical Officer Dame Sally Davies says the screening programme is not a political gesture

Dame Sally also said exercises held earlier on Saturday to test the UK's Ebola response were "vitally important" and would strengthen protection plans.

She said lessons would be learned from the "realistic" eight-hour drill which had tested the response of the government and the emergency services.

Health Secretary Jeremy Hunt said he was "doubly reassured" that the government had "robust plans" in place in the event of an Ebola case in the UK and that the exercise was just part of this.

"We will evaluate what went well and what we need to improve," he added.

Actors simulated symptoms, medical staff wore full protective suits and the health secretary chaired a mock emergency meeting.

In one test scenario, paramedics had a call about someone who had collapsed at Gateshead shopping centre. The patient was initially taken to Newcastle then transferred to a specialist isolation unit at the Royal Free Hospital in London when Ebola was suspected.

In the other simulated case, a patient visited a walk-in centre in Hillingdon, London, with flu-like symptoms having recently returned from West Africa. After blood tests the patient was taken to the Royal Free.

In other developments:

The Spanish nurse infected with Ebola at a Madrid hospital, Teresa Romero, improved overnight and is talking, medical sources say

Macedonian officials say test results have proved a British man previously thought to have died of Ebola did not have the virus

The Confederation of African Football says it has no plans to change the January-February schedule of the African Nations Cup, after hosts Morocco called for a postponement over Ebola fears

The UN special envoy on Ebola, Dr David Nabarro, has warned that the world might have to live with the disease forever unless almost every country is mobilised to fight it

Liberian health workers say they will go on strike on Monday if the government has not resolved the issue of risk and hazard allowance paid to them by then

Ebola symptoms: What to do in the UK

Image copyright Reuters Image caption The Royal Free Hospital in London has a unit for treating any UK Ebola patients

Symptoms of Ebola include fever, headache, vomiting, diarrhoea and bleeding - but these are similar to more common infections like flu and some stomach bugs.

If you have these symptoms and have had contact with an Ebola patient, ring 111 first. Do not go directly to A&E or a GP.

If there has been no contact with Ebola, seek help from 111, your GP or A&E if necessary.

The chances of developing Ebola in the UK are low.

Figures from the World Health Organization show there have been 4,024 confirmed or suspected Ebola deaths in the worst-affected West African nations of Guinea, Liberia and Sierra Leone during the current outbreak.

There have been 8,399 confirmed or suspected cases in total, mostly in West Africa.

As part of the UK effort to help contain the outbreak, 750 military personnel and the Royal Fleet Auxiliary Argus, a medical ship, are being sent to West Africa.

RFA Argus, which has a fully-equipped hospital including critical care and high-dependency units, is being loaded with supplies at Falmouth in Cornwall and will leave for Sierra Leone next week.

It will travel with three Merlin helicopters, aircrew and engineers to provide transport and support to medical teams and aid workers.

Image copyright Ministry of Defence Image caption RFA Argus is part of the UK effort to help tackle the Ebola outbreak

Personnel from the Army's 22 Field Hospital have been training in York and are expected to be sent to west Africa in the coming weeks to run a 12-bed facility specifically to treat medics who have caught Ebola.

The UK government said it had been at the "forefront" of responding to Ebola, giving £125m in support so far.

It said this would "support 700 treatment beds to aid up to 8,800 patients over six months", help in "shoring up Sierra Leone's stretched public health services" and provide vital supplies including protective clothing.