Third-year medical student Allie Tetreault, left, talks with Gabrielle Nuki, 16, at Maine Medical Center in Portland, Maine. Gabrielle helps med students practice patient care. Patti Wight/MPBN hide caption

itoggle caption Patti Wight/MPBN

Barbara Bush helps a nun to fit on a hearing device during a 2012 event in Gulu, Uganda. She says was interested in architecture as a college student but became a global health activist after visiting East Africa with her parents. Reuters/Landov hide caption

itoggle caption Reuters/Landov

Opponents and supporters of a law that restricts abortion in Texas rallied outside the Texas Capitol in Austin as the bill was debated in July 2013. Eric Gay/AP hide caption

itoggle caption Eric Gay/AP

Peter Piot was one of the co-discoverers of the Ebola virus in 1976. "I never thought we would see such a devastating and vast epidemic," he says. Leon Neal/AFP/Getty Images hide caption

itoggle caption Leon Neal/AFP/Getty Images

A Public Health Agency of Canada worker seen inside the National Microbiology Laboratory's Level 4 lab in Winnipeg. Public Health Agency of Canada/Nature hide caption

itoggle caption Public Health Agency of Canada/Nature

New Yorkers can take city-run classes to learn how to make their homes and businesses less attractive to these guys. Ludovic Bertron/Flickr hide caption

itoggle caption Ludovic Bertron/Flickr