More than 530 deaths in Guinea, Liberia and Sierra Leone have now been attributed to the Ebola virus — the largest outbreak on record.

The key to stopping the spread of the disease, which causes its victims to bleed from the ears and nose, is isolating the sick, but fear and panic have sent some patients into hiding.

Ebola has reached the capitals of all three countries, and the World Health Organization reported 44 new cases including 21 deaths on Friday.

There are reports of panicked residents in remote areas attacking the very health workers who've been sent to help them.

In one town in Sierra Leone, residents partially burned down a treatment center over fears that the drugs given to victims were actually causing the disease.

Dr. Unni Krishnan, who heads disaster preparedness and response for the WHO, says there've been no recorded cases of Ebola outside Africa, and, he says, the "threat of it spreading though is very much there."

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