Dr. Pierre Rollin is an expert on Ebola with the U.S. Centers for Disease Control and Prevention. Two and a half weeks ago he returned from the Democratic Republic of Congo, which is now in the fourth month of an Ebola outbreak.
It's not the first time the disease has struck in Congo. Rollin has been visiting for more than 20 years to respond to periodic Ebola outbreaks. And he says there's a pattern to these eruptions.