WHO declares a worldwide emergency on EBOLA ....

The World Health Organisation has declared the Ebola outbreak an international public health emergency, but it is not recommending general bans on travel or trade.

The global body said the Ebola outbreak – the largest and longest in history – was happening in countries without the resources to manage the infections, some with devastated healthcare systems still recovering from war, and called on the international community to help.

"Countries affected to date simply do not have the capacity to manage an outbreak of this size and complexity on their own," said Margaret Chan, the WHO's director general. "I urge the international community to provide this support on the most urgent basis possible."

The current outbreak began in Guinea in March and has spread to Sierra Leone and Liberia, with some cases in Nigeria. There is no licensed treatment or vaccine for Ebola and the death rate has been about 50%.

The virus has an incubation period of up to 21 days, meaning symptoms do not necessarily show before then.

A World Health Organisation panel of medical ethics experts ruled on Tuesday that it is ethical to offer unproven drugs or vaccines as potential treatments or preventions in West Africa's deadly Ebola outbreak.