A mobile clinic set up to test students for HIV is parked near Madwaleni High School in Mtubatuba, KwaZulu-Natal, South Africa on March 8, 2011. Parts of the South African province have HIV rates that are more than twice the national average.
Stephane de Sakutin/AFP/Getty Images
Health care workers in South Africa speak to residents during a door-to-door AIDS awareness campaign, part of a series of prevention efforts that has helped lower the country's HIV infection rate.
Mujahid Safodien /Reuters /Landov
HIV patient Darnell Hollie, 47, talks to her doctor Monica Gandhi (right) at San Francisco General Hospital. Her path from drug addict to model patient was "a lot of work, but if you want it, it's there for you," Hollie says.
Data from the Twins Early Development Study shows areas in the U.K. where the effect of environmental factors, shown in pink, trumps the influence of genes, shown in blue, and vice versa.
Nurse Susan Peel gives a whooping cough vaccination to a high school student in Sacramento, Calif. The whooping cough vaccine given to babies and toddlers loses much of its effectiveness by the time people reach their teens and early adulthood.