David Quammen Viruses Quotations

We're shaking loose viruses and dislodging them from their natural ecological limitations, places where they aren't very abundant and have competition, even within a single animal. We introduce them into a new, rich habitat called the human population, where they can flourish more abundantly and cause more trouble.

Viruses have to live somewhere. They can only replicate in living creatures. So, when the Ebola virus disappears between outbreaks, it has to be living in some reservoir host, presumably some species of animal.