Bill & Melinda Gates Foundation CEO Susan Desmond-Hellmann talks with The Verge's Walt Mossberg and Recode's Kara Swisher about her efforts to stop Ebola, Dengue fever and the Zika virus in the poorest parts of the world. She explains why Zika rose so rapidly without warning and what affected countries like Brazil and Colombia can do to slow it down. Next on the to-do list: Wiping out African sleeping sickness.