Red Cross volunteers prepare to bury the body of an Ebola victim in Pendembu, Sierra Leone, early this month. Tommy Trenchard for NPR hide caption

itoggle caption Tommy Trenchard for NPR

Usman (right), 7 months, and Abdullah (left), 18 months, are held by their mothers while they wait to receive the polio vaccine at the Jalozai refugee camp near Peshawar, Pakistan. Daniel Berehulak/Getty Images hide caption

itoggle caption Daniel Berehulak/Getty Images

During nationwide polio campaigns, hundreds of thousands of health workers go door to door, giving children two drops of the polio vaccine. Anadolu Agency/Getty Images hide caption

itoggle caption Anadolu Agency/Getty Images

Medical workers treat Ebola patients at the Eternal Love Winning Africa hospital in Monrovia, Liberia. Three workers at the hospital, including Dr. Kent Brantly (left), have tested positive for Ebola. Courtesy of Samaritan's Purse hide caption

itoggle caption Courtesy of Samaritan's Purse

A health worker gives a child the polio vaccine in Bannu, Pakistan, June 25. More than a quarter-million children in Taliban-controlled areas are likely to miss their immunizations. A. Majeed/AFP/Getty Images hide caption

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Dr. Kent Brantly (right) of Samaritan's Purse gives orders to treat Ebola patients through the doorway of the isolation ward in Monrovia, Liberia. Courtesy of Samaritan's Purse hide caption

itoggle caption Courtesy of Samaritan's Purse

Clear and clean, bubble wrap is well-suited to serve as an array of tiny test tubes. Here a dye solution is injected into the bubbles to measure the hemoglobin concentration in blood. American Chemical Society hide caption

itoggle caption American Chemical Society

An Indian woman takes tuberculosis pills at a clinic in Mumbai. More than 700 Indians die from TB each day. That's one death every two minutes. Pal Pillai/AFP/Getty Images hide caption

itoggle caption Pal Pillai/AFP/Getty Images

Construction workers repair the roof inside the isolation area at the Doctors Without Borders treatment center in Kailahun. Tommy Trenchard for NPR hide caption

itoggle caption Tommy Trenchard for NPR

Dogs throughout Latin America carry the Chagas parasite — and boost the risk of people catching it. And it's not just shelter dogs, like these in Mexico, who are at risk. Even family dogs get the deadly disease. Jose Luis Gonzalez /Reuters/Landov hide caption

itoggle caption Jose Luis Gonzalez /Reuters/Landov