JEFFREY BROWN:

Dr. Kevin De Cock, thanks for talking to us.

There is a report that a new estimate is in the works that may have a worst-case scenario of as high as half-a-million people. Can you comment on that?

DR. KEVIN DE COCK, Centers for Disease Control and Prevention: Yes.

The doubling time of new cases of Ebola virus disease in Liberia is about every 20 days. So there is a total number of cases doubling about every three weeks. We're now up to 3,000, 4,000 cases, reported cases, which may be a slight underestimate.

So, very rapidly, we do expect to see some tens of thousands of cases, and quite possibly, by the end of the year, early next year, some hundreds of thousands, unless this is — unless this is slowed down.