Liu, a Canadian-born physician, has worked with MSF since 1996, when she took on her first field assignment: caring for Malian refugees in Mauritania. Since then she has taken part in more than 20 missions on four continents—helping victims of the Indonesian tsunami and Haitian earthquake, as well as refugees and survivors of sexual violence in Somalia, Congo, and Sudan’s Darfur region, to name just a few. But Liu’s job got even more demanding in October 2013, when she was named the group’s international president just two months before the first West African patients were diagnosed with Ebola, the start of what became the deadliest and most widespread outbreak of the horrific disease to date. Liu and MSF didn’t dither for a second. She helped lead the organization’s fast and aggressive response to the virus, establishing field hospitals in the middle of the hot zone and pressing African leaders and public health officials worldwide to step up their efforts. The pressure worked. At least for the time being, this contagion has been contained.