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

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

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

Oxana and Pavel Rucsineanu walk to the tuberculosis hospital in Balti, Moldova. Oxana and their new baby live in an apartment, but Pavel still has to stay at the TB ward, fighting for his life. Jason Beaubien/NPR hide caption

itoggle caption Jason Beaubien/NPR

A health worker weighs a Somali baby on scales at a medical clinic in Mogadishu. Babies in Somalia have the highest risk of dying within the first 24 hours after birth. Carl de Souza/AFP/Getty Images hide caption

itoggle caption Carl de Souza/AFP/Getty Images

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

itoggle caption Ben Curtis/AP

An extract of sweet wormwood has been used in China for thousands of years to treat malaria, but being able to make mass quantities of the extract has been elusive, until now. Sarah Cuttle/Getty Images hide caption

itoggle caption Sarah Cuttle/Getty Images

Dengue fever patients are treated in a hospital in Asuncion, Paraguay, in January. Norberto Duarte/AFP/Getty Images hide caption

itoggle caption Norberto Duarte/AFP/Getty Images

A child is immunized against polio at the health clinic in a farming village in northern Nigeria. The procedure involves pinching two drops of the vaccine into the child's mouth. For full protection, the child needs three doses, spaced out over time. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

The city of Sao Paolo, Brazil, shot with a fisheye lens. Standards of living are improving not just in the big developing nations like Brazil, but also in smaller countries such as Bangladesh and Ghana. Daniel Incandela/Flickr via Wikimedia Commons hide caption

itoggle caption Daniel Incandela/Flickr via Wikimedia Commons