Colored brain scan of a 17-year-old boy with mad cow disease. The bright yellow spots are a sign that the thalamus is damaged by diseased proteins. Simon Fraser/Science Source hide caption

itoggle caption Simon Fraser/Science Source

At her home in the U.K., Malala Yousafzai reads her letter to the missing Nigerian schoolgirls. Courtesy of Malala Fund hide caption

itoggle caption Courtesy of Malala Fund

A year ago, Lina says her parents took her to Yemen because her grandmother was gravely ill. But when the family arrived, Lina's father announced that she would be getting married to a local man. Renee Deschamps/Getty Images/Vetta hide caption

itoggle caption Renee Deschamps/Getty Images/Vetta

Secretary of State John Kerry and African Union Commission Chairperson Nkosazana Dlamini Zuma signed an agreement Monday to establish the first Centers for Disease Control and Prevention in Africa. The U.S. will provide technical advice and a few staff for the agency. Alex Wong/Getty Images hide caption

itoggle caption Alex Wong/Getty Images

In March, demonstrators in Nairobi demanded tougher punishment for assailants of women and girls. Anadolu Agency/Getty Images hide caption

itoggle caption Anadolu Agency/Getty Images

Rio has hosted competitions that include athletes with physical impairments (above: the open water swim at Copacobana beach for the Rei e Rainha do Mar). But there's never been an event on the scale of the Paralympics. Buda Mendes/Getty Images hide caption

itoggle caption Buda Mendes/Getty Images

The health workers of Sierra Leone — like Dr. Komba Songu M'Briwah (on the phone) — were dedicated to fighting Ebola. But they had a huge handicap. A government report reveals that some of the money allocated went to pay "ghost workers." David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

No one knows how many children have been affected by the spread of Boko Haram across Nigeria and neighboring countries. This photo shows the school uniforms of the girls kidnapped from a school a year ago. Glenna Gordon/Glenna Gordon for NPR hide caption

itoggle caption Glenna Gordon/Glenna Gordon for NPR

A police officer is silhouetted through the emergency room door at a public hospital in San Pedro Sula, Honduras. With 91 murders per 100,000 people, the Central American nation is often called the most violent in the world. The homicide rate is roughly 20 times that of the U.S. rate, according to a 2011 U.N. report. Esteban Felix/AP hide caption

itoggle caption Esteban Felix/AP