The deadly Ebola virus which has killed hundreds of people in West Africa is mutating at a rate which could hamper efforts to find a cure, researchers have warned.
Genetic studies of some of the earliest Ebola cases in Sierra Leone have found more than 300 changes in the virus as it moved from person to person.
The findings, published in Science, suggest current diagnostics and potential treatments and vaccines may struggle to keep up.
The study examined samples from 78 people in Sierra Leone, where the infections could all be traced to one faith healer who claimed to have found a cure, attracting affected patients from Guinea.
As it reaches seven months since the Ebola outbreak started we take a look at the timeline of events leading up to the spread of the virus.
More than 100 British personnel are arriving in Sierra Leone to combat the Ebola outbreak in West Africa. Here's what else the UK is doing.
A man has been filmed helping an Ebola patient onto a plane without wearing any protective equipment.