Neudy Rojop decided to work in public health when she was a young girl observing how frequently her young family members and neighbors got sick with unknown illnesses. Luis Echeverria for NPR hide caption

Wielding the "insectazooka," Cecilia González prepares to collect mosquitoes from a house in the village of Los Encuentros, Guatemala. Luis Echeverria for NPR hide caption

A field researcher holds a male bat that was trapped in an overhead net as part of an effort to find out how the animals pass Nipah virus to humans. The animal will be tested for the virus, examined and ultimately released. Fatima Tuj Johora for NPR hide caption

Until the 19th century, scientists did not understand the role of hand-washing in disease prevention. Thomas Lohnes/DDP/AFP via Getty Images hide caption

Computer generated illustration of the moment a bacteriophage lands onto the surface of a bacterium. NANOCLUSTERING/SCIENCE PHOTO LIB/Getty Images/Science Photo Libra hide caption

Computer generated illustration of the moment a bacteriophage lands onto the surface of a bacterium. NANOCLUSTERING/SCIENCE PHOTO LIB/Getty Images/Science Photo Libra hide caption

Justine Adhiambo Obura, chairwoman of the No Sex For Fish cooperative in Nduru Beach, Kenya, stands by her fishing boat. Patrick Higdon, whose name is on the boat, works for the charity World Connect, which gave the group a grant to provide boats for some of the local women. Julia Gunther for NPR hide caption

A pile of debris including all kinds of plastics grows hourly at Omni Recycling, a materials recovery facility in Pitman, N.J. Plastic bags are especially problematic because they can get caught in the conveyor belts and equipment and gum up the recycling process. Rebecca Davis/NPR hide caption

In 2011, a 17-year-old named Mishka told readers of his Facebook post that his Salem, Ore., high school was "asking for a f***ing shooting." That post and other furious outbursts triggered a quick, but deep evaluation by the school district's threat assessment unit. Beth Nakamura for NPR hide caption

Aaron Reid, 20, rests in an exam room in the National Institutes of Health Clinical Center in Bethesda, Md. Rebecca Davis/NPR hide caption

Kelly Zimmerman holds her son Jaxton Wright at a parenting session at the Children's Health Center in Reading, Pa. The free program provides resources and social support to new parents in recovery from addiction, or who are otherwise vulnerable. Natalie Piserchio for NPR hide caption

A poster put out by the U.S. Children's Bureau in 1918. Francis Luis Mora/Library of Congress hide caption

Samantha Pierce of Cleveland has a 7-year-old daughter, Camryn. In 2009, Pierce gave premature birth to twins. The babies did not survive. Scientists say black women lead more stressful lives, which makes them more likely to give birth prematurely and puts their babies at risk of dying. Dustin Franz for NPR hide caption