Two US aid workers who contracted the deadly Ebola virus in Liberia given a highly experimental, unapproved drug are now showing signs of recovery, sparking hopes for a treatment.

While it is far too early to be certain that the drug, dubbed ZMapp, is effective, the fact that both patients seem to be fighting the disease - which has a death rate of up to 90% - is very encouraging.

The treatment, a cocktail of three antibodies against Ebola, is being developed by tiny San Diego, USA-based biotech Mapp Biopharmaceutical, which has just nine employees.

Citing sources close to the situation, CNN reported that, within an hour of receiving zMapp, aid worker Kent Brantly's condition “improved dramatically”, as has that of co-worker Nancy Writebol.

The treatment has only been tested on animals so far, but Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases, has told the media that clinical trials are to start in September.

Vaccine next year

Also, by the middle to end of next year a vaccine should be available, at least to protect healthcare workers in the first instance, he told the BBC's Newsday programme.

Almost 900 people have died of Ebola in West Africa since the outbreak began in February. Health officials say the risk of the disease spreading to the US and UK remains low.

British Airways has this week announced a temporary suspension of flights to and from Liberia and Sierra Leone until the end of August as a precaution.