Is Ebola a Stealthy Virus?

The Ebola virus that has killed 4,000 people in west Africa caught everyone by surprise when it erupted thousands of kilometres from its historical hotbed. The outbreak, experts say, revealed just how little we know about the deadly agent. What is the virus' natural range? Are there limits? Can they shift? "Previously we were under the impression that this problem would be predominantly restricted to central Africa. Clearly, that is not ...