The skull of a female Neanderthal, who lived about 50,000 years ago, is displayed at the Natural History Museum in London. Rick Findler/Barcroft Media/Landov hide caption

itoggle caption Rick Findler/Barcroft Media/Landov

When Benta Odeny was diagnosed with HIV, she started to protect her husband Daniel from the virus by taking antiretroviral medications. The same drugs also helped her give birth to an HIV-negative daughter, Angelia. Gregory Warner/NPR hide caption

itoggle caption Gregory Warner/NPR

Sun, shopping and chikungunya? A nasty virus has sickened 10 people on the island of St. Martin in the past few months. Balalaika/iStockphoto hide caption

itoggle caption Balalaika/iStockphoto

A mother waits with her child at an HIV clinic in Nyagasambu, Rwanda, in February 2008. The clinic was built with a grant from the President's Emergency Plan for AIDS Relief initiative. Shashank Bengali/MCT /Landov hide caption

itoggle caption Shashank Bengali/MCT /Landov

A polio worker vaccinates a child in Khyber-Pakhtunkhwa province, Pakistan, in October. Arshad Arbab/EPA/Landov hide caption

itoggle caption Arshad Arbab/EPA/Landov

The chikunguyna virus was discovered in 1955 by two scientists in Tanzania. EMDataBank using UCSF Chimera hide caption

itoggle caption EMDataBank using UCSF Chimera

Children get tested for malaria at a clinic near the Myanmar border in Sai Yoke, Thailand. Drug-resistant strains of the parasite have appeared in the region over the past few years. Surkree Sukplang/Reuters /Landov hide caption

itoggle caption Surkree Sukplang/Reuters /Landov

Syrian boys line up to get the polio vaccine at a refugee camp in Sidon, Lebanon, on Nov. 7. The Lebanese government plans to vaccinate all kids under age 5 for the virus, including Syrian refugees. Mohammad Zaatari/AP hide caption

itoggle caption Mohammad Zaatari/AP

President Obama walks into an auditorium in the Eisenhower Executive Office Building Monday for a speech about World AIDS Day. Carolyn Kaster/AP hide caption

itoggle caption Carolyn Kaster/AP

A child wearing the traditional eyeliner kajal peeps from behind a door in Allahabad, India. Rajesh Kumar Singh/AP hide caption

itoggle caption Rajesh Kumar Singh/AP

One experimental condom has tabs on either side so it's easier to put on in the dark. Courtesy of California Family Health Council hide caption

itoggle caption Courtesy of California Family Health Council

Yoset, a spiritual healer near Arua, Uganda, works with the Centers for Disease Control and Prevention to detect the plague in his village. Courtesy of Mary Hayden hide caption

itoggle caption Courtesy of Mary Hayden

Young students in a Bridge International Academy school in Nairobi, in September. On the surface, there's little to distinguish these schools from others in the developing world. But Bridge's model relies on teachers reading lessons from tablets. Frederic Courbet for NPR hide caption

itoggle caption Frederic Courbet for NPR

Military personnel from the U.S. and the Philippines unload relief goods at the Tacloban airport, Nov. 11, 2013. Some reports estimate that 10,000 people may have died in the city of Tacloban. Ted Aljibe/AFP/Getty Images hide caption

itoggle caption Ted Aljibe/AFP/Getty Images