More than one million people have been affected by the current Ebola outbreak in west Africa and there is "no early end in sight", the World Health Organisation (WHO) has warned.

"This is an extraordinary outbreak that requires extraordinary measures for containment. This is a severe health crisis, and it can rapidly become a humanitarian crisis if we do not do more to stop transmission," WHO director-deneral Margaret Chan said during a briefing in Geneva on Wednesday. Those affected, Chan said, needed daily material support, including food.

According to the latest WHO update, 128 new cases of Ebola virus disease, as well as 56 deaths, were reported from Guinea, Liberia, Nigeria, and Sierra Leone between August 10 and 11, bringing the total number of cases to 1,975 and deaths to 1,069.

"The outbreak is unprecedented in its size, severity, and complexity. Cases are occurring in remote rural areas that are difficult to access, but also in capital cities," she said, adding that agencies like MSF (Doctors without Borders) were finding it difficult to reach staff and supplies in isolated zones.

She also expressed concern over the "unprecedented" number of healthcare workers infected by the virus — 170 so far, of whom 80 have died.

UN secretary-general Ban Ki-moon appointed David Nabarro as senior UN system coordinator for Ebola which has been designated a "public health emergency of international concern". Nabarro will be responsible for ensuring the UN system makes an effective and coordinated contribution to the global effort to control the outbreak.