HuffPost Live examines everything you need to know about lethal disease that has killed hundreds of people in West Africa, in its worst ever outbreak.
Fears have been raised that the disease could spread beyond West Africa after a man who flew from one of the affected countries - where the borders have only just been closed - later died.
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Patrick Sawyer died in the Nigerian city of Lagos, Africa's largest, which is far better connected to the outside world than the rural areas of Sierra Leone, Liberia and Guinea where the outbreak has been raging since March, killing around 670 people so far.