The death toll from the Ebola virus outbreak has risen to 4,447, with the large majority of victims in West Africa, the World Health Organization (WHO) says.

The WHO says a slowdown in the rate of new cases in some areas may be due to behavioural changes

WHO assistant director-general Bruce Aylward also said there could be up to 10,000 new cases a week within two months if efforts were not stepped up,

But the rate of new infections in some areas has slowed down, he added.

Sierra Leone, Liberia and Guinea have been hardest hit by the outbreak.

There have been 8,914 cases overall, including the fatal cases, and the WHO says it expects this number to top 9,000 by the end of the week.

The WHO estimates its figures by taking the numbers of confirmed cases and multiplying them - from Guinea by 1.5, from Sierra Leone by 2 and from Liberia by 2.5 - to account for under-reporting.

In other developments:

•    The UK begins Ebola screening at London's Heathrow airport

•    A medic working for Sierra Leone's army at a peacekeeping training centre in Freetown tests positive for Ebola

•    A "site manager" is appointed at the Dallas hospital where a nurse was infected, with the task of supervising how workers put on and take off protective clothing

•    The US Centers for Disease Control and Prevention has set up an immediate response team to travel to any US hospital where Ebola is diagnosed, to hit the ground "within hours"

•    A UN health worker, originally from Sudan, dies in Germany after contracting the disease in Liberia

•    Facebook co-founder and chief executive Mark Zuckerberg says he and his wife, Priscilla Chan, are donating $25m (£16m) to fight Ebola

•    A Spanish nurse - the first person to contract the disease outside of Africa - remains in critical condition, although doctors say there are signs of improvement

Source: BBC