BAMAKO, Mali—I was talking to Yaya Sarro, a molecular biologist at the National Laboratory, when the biological samples from the newest possible Ebola case arrived for diagnosis. It was six days after Mali’s first patient, a two-year old girl who had taken a long bus ride from Guinea with her grandmother and sister, tested positive for Ebola. She died on Oct. 24, 600 km northwest of the capital in Kayes. Now Malians, hospital staff, contact tracers, the ministry of health, a few journalists and a coalition of international partners were anxiously waiting for the next case to appear. Eighty-five people were under surveillance, mostly in Kayes, but some in the capital. Families were in isolation.