The number of suspected cases of Ebola has risen to 29 from nine in less than a week in an isolated part of Democratic Republic of Congo, where three people have died from the disease since April 22, the World Health Organization said on Thursday. The W.H.O. was criticized for responding too slowly to an outbreak in West Africa in 2014 that left more than 11,000 people dead, and Dr. Peter Salama, the executive director of the organization’s health emergencies program, said at a briefing that it was essential to “never, ever underestimate Ebola” and to “make sure we have...