It has been three years since the United Nations declared an Ebola outbreak in parts of West Africa.

Yet doctors still do not know how the virus was passed from animals to humans.

More than 10,000 people died from the disease across the region.

Doctors in Liberia are now testing a new vaccine on survivors.

Al Jazeera's Nicolas Haque reports from Liberia’s capital, Monrovia.

Africa, Liberia, Health