Ebola , Frieden chief : U.S. health system has been preparing since 21 days for first U.S. Ebola case . Clear differences between Ebola in Africa and what will happen in U.S. , says Tom Frieden . The U.S. health system has been preparing since late March for the news we announced Tuesday : the first case of Ebola diagnosed in the United States . March is the longest known incubation period for Ebola , Frieden says .
Ebola , Frieden chief : U.S. health system has been preparing since 21 days for first U.S. Ebola case . Clear differences between Ebola in Africa and what will happen in U.S. , says Tom Frieden . March is the longest known incubation period for Ebola , Frieden says .