Almaz Acha sits with her baby Alentse at her home in the rural community of Sadoye, in southern Ethiopia. Families in rural communities, like this one, have benefited from Ethiopia's health extension program. Julien Behal/PA Photos /Landov hide caption

itoggle caption Julien Behal/PA Photos /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 simulated patient at the University of Malaya makes use of different materials to mimic the look and feel of human tissue. /Courtesy of Vicknes Waran hide caption

itoggle caption /Courtesy of Vicknes Waran

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

Developing a vaccine for meningitis B was tricky. Even the existing vaccine doesn't protect against all B strains. Josef Muellek/iStockphoto.com hide caption

itoggle caption Josef Muellek/iStockphoto.com

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

The Ivy League school has begun vaccinating nearly 6,000 students to try to stop an outbreak of type B meningitis in an unusual federal government-endorsed administration of a drug not generally approved for use in the U.S. Mel Evans/AP hide caption

itoggle caption Mel Evans/AP

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