More than 120 health workers have died of Ebola across west Africa, the World Health Organization said tonight.

It claimed the epidemic had affected an "unprecedented number of medical staff".

In a statement, the WHO said more than 240 health care workers working in Guinea, Liberia, Nigeria, and Sierra Leone have developed the disease with "more than 120" succumbing to the epidemic.

Meanwhile, the family of a British volunteer nurse repatriated from Sierra Leone after contracting the deadly Ebola virus said today he was in the best place possible for treatment.

William Pooley, 29, is the first Briton to test positive for the haemorrhagic fever in the recent epidemic.

It has killed almost 1,500 people, mostly in Sierra Leone, Liberia and Guinea, in the deadliest outbreak of the disease to date.

Mr Pooley was flown home from West Africa yesterday in a specially adapted Royal Air Force cargo plane and transported to an isolation unit at the Royal Free Hospital in London.

"Will is receiving excellent care at the Royal Free Hospital and we could not ask for him to be in a better place," his family said in a statement, praising the speed at which he was brought home and asking the media to respect their privacy.
"We would like to thank all our family and friends for their best wishes and ask everyone to remember those in other parts of the world suffering with Ebola who do not have access to the same healthcare facilities as Will."
British health officials say strict protective measures have been taken to minimise the risk of transmission while transporting and treating Mr Pooley.
A spokeswoman from Britain's Department of Health said British officials were trying to locate supplies of experimental therapies being used to treat Ebola but any decision to use them would be made by the clinicians and the patient.
Mr Pooley's colleagues praised the bravery of the healthcare worker, who was reported to have been working as a volunteer at a hospice in Sierra Leone's capital Freetown since March before volunteering at an Ebola centre in Kenema five weeks ago.

'The fight against Ebola may take six months'

UN System Coordinator Dr David Nabarro has said the fight against Ebola is a "war" which has not yet been won and could take another six months.

Speaking at a news conference today in Freetown, Sierra Leone, Dr Nabarro said "I hope it will be done in six months but we have to do it until it is completed."

The British physician said airlines halting flights to and from the countries afflicted by the outbreak in west Africa were making the UN's efforts "a whole lot harder".

Japan ready to offer trial Ebola drug

Elsewhere, Tokyo stands ready to offer an experimental drug developed by a Japanese company to help stem the global tide of the deadly Ebola virus, the top government spokesman has said.

"Our country is prepared to provide the yet-to-be approved drug in cooperation with the manufacturer if the WHO requests," Chief Cabinet Secretary Yoshihide Suga.

The World Health Organization has been discussing the use of unapproved drugs as a way of getting a handle on an outbreak in Africa that has already cost more than 1,400 lives, with thousands more people infected.

There is currently no available cure or vaccine for Ebola, and the WHO has declared the latest outbreak a global public health emergency. Several drugs are under development.

The use of an experimental drug called ZMapp on two Americans and a Spanish priest infected with the virus while working in Africa has opened up an intense ethical debate.

The drug, which is in very short supply, has reportedly shown promising results in the two Americans, although the priest died.

US company Mapp Bioparmaceutical, which makes the drug, said this month it had sent all its available supplies to west Africa. 

WHO earlier said a panel of medical experts had determined it is "ethical" to provide experimental treatments.

"Even before the WHO reaches a conclusion, we are ready to respond to individual requests [from medical workers] under certain conditions if it is an urgent case," Mr Suga said this afternoon.

The medication Mr Suga was referring to is Avigan, a drug in tablet form that was approved as an anti-influenza drug in Japan in March and is currently in clinical tests in the United States.

Its developer Fujifilm Holdings said it had received inquiries from abroad but declined to say how many and from which countries.

The company, which has diversified into healthcare fields, has "no problem" over the amount of stockpiles, according to spokesman Takao Aoki.

"We have sufficient supplies for more than 20,000 people," he said.