Health workers vaccinate a boy against polio at a May immunization drive in Mogadishu, Somalia. Farah Abdi Warsameh/AP hide caption

itoggle caption Farah Abdi Warsameh/AP

A woman sells bananas at the Kampala Airport. Ugandans eat about a pound of the fruit, on average, per day. Ronald Kabuubi/AP hide caption

itoggle caption Ronald Kabuubi/AP

Saudi men walk to the King Fahad hospital in the city of Hofuf on Sunday. In eastern Saudi Arabia, where outbreaks of the MERS virus have been concentrated, people have resumed their habits of shaking hands and kissing. Fayez Nureldine/AFP/Getty Images hide caption

itoggle caption Fayez Nureldine/AFP/Getty Images

Two women in Colombo, Sri Lanka, attend a March protest calling for government action against domestic violence and rape. Dinuka Liyanawatte/Reuters /Landov hide caption

itoggle caption Dinuka Liyanawatte/Reuters /Landov

A woodcut from the 1800s, Healing the Lepers, depicts the common tableau of Jesus healing a leper as his disciples look on. Images from the History of Medicine hide caption

itoggle caption Images from the History of Medicine

Boys at the L'Ecole Les Freres Clement elementary school in Jacmel, Haiti, line up to take deworming pills that protect against elephantiasis. Maggie Steber for The Washington Post/Getty Images hide caption

itoggle caption Maggie Steber for The Washington Post/Getty Images

A public health poster from 1952 encourages Americans to get checked for sexually transmitted diseases. Gonorrhea is the second-most-common sexually transmitted disease in the U.S., with more than 300,000 cases reported in 2011. Images from the History of Medicine hide caption

itoggle caption Images from the History of Medicine

Men outside a hospital in Dammam, Saudi Arabia, wear surgical masks as a precaution against infection with a coronavirus. Stringer/Reuters /Landov hide caption

itoggle caption Stringer/Reuters /Landov

Students paste red ribbons on a window to mark World AIDS Day in Nanjing, China, in 2006. Although many infectious diseases have declined in the country, the number of new HIV cases nearly quadrupled between 2007 and 2011. AP hide caption

itoggle caption AP

A vendor weighs a live chicken at the Kowloon City Market in Hong Kong last April. After closing live poultry shops in many cities around China, the rate of new H7N9 infections sharply declined. Lam Yik Fei/Getty Images hide caption

itoggle caption Lam Yik Fei/Getty Images

Michelle Williams (center) and two daughters visit the grave of her mother, Judy Williams, at Fairview Cemetery in Hyde Park, Mass., on May 11. Judy died in 2011. Ellen Webber for NPR hide caption

itoggle caption Ellen Webber for NPR

A nurse walks towards the Roger Salengro Hospital in Lille, France, where two patients were diagnosed with a coronavirus related to SARS. Michel Spingler/AP hide caption

itoggle caption Michel Spingler/AP

A baby receives a polio vaccine at the Medina Maternal Child Health center in Mogadishu, Somalia. The country has one of the lowest immunization rates in the world. Ben Curtis/AP hide caption

itoggle caption Ben Curtis/AP