Image copyright PA Image caption Personnel from the British army's 22 Field Hospital have been training, as wider UK exercises are planned

A national exercise is taking place to test how the UK would deal with a potential outbreak of the Ebola virus.

In the eight-hour exercise, actors in various parts of the UK are simulating symptoms to test the responses of emergency services and the government.

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.

Passenger screening is to be introduced at key UK airports and rail terminals.

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.

As part of the UK effort to help contain the outbreak, the Royal Fleet Auxiliary Argus, a medical ship, is being loaded with supplies in Falmouth ahead of a mission to Sierra Leone.

Meanwhile, Macedonian officials have said test results have proved a British man suspected to have died of Ebola did not have the virus.

'Vital' test

The national exercise, ordered by Prime Minister David Cameron, is expected to include a simulated meeting of the government's Cobra emergency committee, to be chaired by Health Secretary Jeremy Hunt.

Some hospital staff were expected to wear personal protective equipment during the exercise.

A Department of Health spokesman said officials had been planning the response to an Ebola case in the UK for "many months".

"It is vital that we test these plans in as realistic a situation as possible - with real people," the spokesman said.

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.

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

Ebola dead 'dangerous'

Image copyright AFP Image caption Sierra Leone is one of the countries affected by the Ebola virus outbreak

Dr David Nabarro, UN special envoy on Ebola, said "just about every country in the world", and many non-governmental organisations, needed to support afflicted countries, otherwise it would be "impossible" to get the virus quickly under control.

If this was not done, he said, the world "will have to live with the Ebola virus forever".

"This is a real challenge to all of us that's going to require every piece of ingenuity and collective action that we can mount," he told the UN.

Dr Nabarro said in many of the West African communities affected, the day of death was one of important rituals which, if not observed, undermined "the very fabric of society".

"Yet people who are dying of Ebola are very dangerous and if they're touched and if they're held at that moment of death they can infect large numbers of other people," he said.

The government this week said people arriving from areas hit by Ebola would face "enhanced screening" at Heathrow and Gatwick airports, as well as at Eurostar terminals.

Ministers initially said there were no plans to screen people arriving from Liberia, Guinea and Sierra Leone.

However, a Downing Street spokesman said the decision to introduce Ebola screening had been based on advice from the Chief Medical Officer, Dame Sally Davies.

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.

Risk 'very low'

Passengers will be asked questions and potentially given a medical assessment during the screening process, Downing Street said.

The Department of Health said further details about how passengers will be checked will be announced next week before the measures come into effect.

In a statement it said "government departments, health protection agencies and the transport sector are continuing to work closely together to minimise the risk" of the virus.

"It is important to stress that given the nature of this disease, no system could offer 100% protection from non-symptomatic cases but the overall risk to the public in the UK remains very low," the statement said.

Mr Cameron said it was right to take action "to keep our own people safe" from Ebola.

Media playback is unsupported on your device Media caption PM David Cameron says ministers are "taking all the steps we can to keep our own people safe"

"What we do is we listen to the medical advice and we act on that advice and that's why we're introducing the screening processes at the appropriate ports and airports," he said.

Mr Cameron said the government was focussed on taking action "right across the board to deal with this problem at source".

"We're making a bigger contribution than almost any other country, in West Africa, to help deal with the crisis at its source," he said.

'Delays and disruption'

However, David Mabey, professor of communicable diseases at the London School of Hygiene and Tropical Medicine, said the screening was a "complete waste of time".

There are currently no direct flights to the UK from the affected areas, but people can fly via Paris or Brussels.

"Are they going to screen everyone from Brussels, Paris, Frankfurt and Amsterdam? That would lead to a lot of delays and disruption," he said.

Image caption RFA Argus is being loaded with supplies in Falmouth, Cornwall

More than 750 military personnel and RFA Argus are being sent to West Africa to help in efforts to contain the outbreak.

RFA Argus, which has a fully equipped hospital including critical care and high-dependency units, 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.

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.