Media playback is unsupported on your device Media caption British army medics are travelling to Sierra Leone, as Richard Lister reports

British army medics have arrived in West Africa to help in the fight against the deadly Ebola virus.

Ninety-one medics from 22 Field Hospital in Aldershot will run a treatment centre in Sierra Leone, set aside for workers who risk infection.

The nurses, doctors and infectious disease consultants join 40 soldiers already in the West African country.

The virus has killed about 4,500 people so far, with nearly all of the deaths in Liberia, Guinea and Sierra Leone.

The army medics arrived ahead of the departure of UK's casualty vessel RFA Argus on Friday.

The Royal Navy ship, which has a fully-equipped hospital, is expected to reach the region by the end of the month with 225 military personnel onboard from a total planned deployment of 750.

Prime Minister David Cameron, meanwhile, is expected to chair the latest meeting of the government's emergency Cobra committee to discuss the UK's response.

Experts have previously warned the UK can expect some cases of Ebola but the risk to the public remains low.

Heathrow has begun screening passengers from affected countries but Deputy Prime Minister Nick Clegg rejected suggestions this should be implemented for all arrivals, or that inbound flights should be halted.

"I just don't think we can put up a 'no entry' sign across the whole of the United Kingdom. We can't seal ourselves off," he said on his LBC Radio phone-in show.

Image copyright PA Image caption The UK's 22 Field Hospital prepares to fly out to Sierra Leone

The UK personnel, who are based at Kerrytown, around 30 miles from Freetown, the capital of Sierra Leone, received nine days of intensive training in treating those affected with the disease.

The treatment unit will contain 12 beds and run alongside a facility which will eventually be run by Save the Children.

Lieutenant Colonel Alison McCourt, of 22 Field Hospital at Normandy Barracks in Aldershot, said: "We need to provide sufficient reassurance to healthcare workers that will encourage them to come and help defeat this disease.

"This unit has been the 'Vanguard' medical regiment for the past 20 months which means we are on high readiness to deploy at short notice to anywhere in the world - although this is a bit different and provides us with a challenge, we are perfectly suited to this kind of task.

"I firmly believe we can make a significant difference."

The deployment came as the World Health Organization said a major outbreak of the deadly virus in the US and elsewhere in the West was unlikely given the strong health systems there.

The US is also investigating how a nurse infected when treating a victim in Texas was allowed to travel on a plane.

'Serious emergency'

In a video conference call between Mr Cameron, US president Barack Obama and the leaders of Germany, France and Italy on Wednesday, it was agreed the world faced "the most serious international public health emergency in recent years" and the international community "needed to do much more and faster to halt the rise of the disease", said Downing Street.

The most urgent priorities included "increasing the amount of international spending on the issue, increasing the number of trained personnel working in the region to treat those affected and prevent the disease spreading and evacuation procedures for workers affected".

The UK government has pledged £125m "to help contain, control, treat and defeat Ebola" and 659 front-line NHS staff and 130 Public Health England staff have volunteered to travel to West Africa.

In the UK, passengers arriving at Heathrow from countries at risk of the virus are being screened for symptoms. They are having their temperatures taken, completing risk questionnaires and having their contact details recorded.

Screening at Gatwick and the Eurostar is expected to be in place next week.

Downing Street has again defended the decision to introduce screening, describing it as an "extra level of protection".

A spokeswoman for the prime minister said no system was foolproof and the measures would be kept under review.

Meanwhile, the Scottish government held a meeting on Wednesday night to discuss the country's response to the outbreak.

First Minister Alex Salmond said the risk of a case remained low but he was confident the health service was "well prepared" for any potential cases.

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