Baba Ahmed

Mali on Saturday confirmed a new case of Ebola and said two more suspected patients are being tested, raising concern about a further spread of the disease which has already killed at least five people in the country.

On Mali’s dusty border with Ebola-stricken Guinea, travelers have a new stop: Inside a white tent, masked medical workers zap incomers with infrared thermometer guns and instruct them to wash their hands in chlorinated water.

It all started with a sick nurse, whose positive test for Ebola came only after her death. In a busy clinic that treats Mali’s elite as well as wounded U.N. peacekeepers, what patient transmitted the virus?