A patient is pictured at a camp for diarrhea patients in Dhaka, Bangladesh. Among the past nominations for untold story: the need for vaccines to prevent "severe, deadly diarrhea" in this part of the world. Zakir Hossain Chowdhury/Barcroft Media via Getty Images hide caption
A trio of toilets, photographed by Samantha Russell, a Peace Corps volunteer, in Viti Levu Island, Fiji. Samantha Russell/Courtesy of PATH hide caption
A young woman is tested for HIV at a health clinic in Uganda. During the presidency of George W. Bush, the U.S. substantially ramped up spending on HIV/AIDS programs abroad — a commitment that retains strong bipartisan support to this day. Per-Anders Pettersson/Getty Images hide caption
Sudanese dockers unload a U.S. aid shipment at Port Sudan on the Red Sea coast on May 5. Ashraf Shazly/AFP/Getty Images hide caption
An image of the Ebola virus taken by an electron microscope. Scott Camazine/Getty Images/Science Source hide caption
Robert Langdon (Tom Hanks) and Sienna Brooks (Felicity Jones) try to evade a drone in Boboli Gardens in Inferno. Jonathan Prime/Sony PIctures hide caption
Men protesting in support of more money for AIDS research marched down Fifth Avenue during the 14th annual Lesbian and Gay Pride parade in New York in 1983. Mario Suriani/AP hide caption
An Indian pedestrian checks his mobile phone in front of an advertisement for a burger of a fast-food giant in Mumbai, India. Fast food and highly processed foods and sodas are increasingly becoming more popular around the world, one of the main reasons for increasing rates of overweight and obesity. Indranil Mukherjee/AFP/Getty Images hide caption
Facebook CEO Mark Zuckerberg and his wife, Dr. Priscilla Chan, have a new goal: cure, manage or eradicate all disease by the end of this century. And they're putting up $3 billion. Jeff Chiu/AP hide caption
Rebecca Richards-Kortum is a "genius grant" winner with a very busy schedule. The engineering professor, who encourages students to come up with medical devices that will be valuable in the developing world, is the mother of six and a marathon runner. John D. and Catherine T. MacArthur Foundation hide caption
Chickens at a poultry farm in Hefei, eastern China. Antibiotics are often used to keep them healthy in densely packed quarters. STR/AFP/Getty Images hide caption
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A vampire bat's fangs are so sharp that victims hardly notice when the animal slices through their skin and starts drinking blood. Bruce Dale/National Geographic/Getty Images hide caption
An Afghan boy carries a sheep on his shoulder at a livestock market on September 22, 2015, just ahead of the Eid al-Adha festival in Kabul. Shah Marai/AFP/Getty Images hide caption