Studies show that only about 40 percent of health care workers in the U.S. wash their hands as often as they should. Rob Carr/AP hide caption

itoggle caption Rob Carr/AP

A woman receives treatment in a U.S.-run emergency clinic in Port-au-Prince. John W. Poole/NPR hide caption

itoggle caption John W. Poole/NPR

According to a new study, people who smoke menthol cigarettes seem to have more difficulty quitting than those who smoke regular cigarettes. iStockphoto.com hide caption

itoggle caption iStockphoto.com

The red specks highlight where the integrity of the brain's white matter is significantly less in the teens who binge drink, compared to those who do not. Courtesy of Susan Tapert/Tim McQueeny/UCSD hide caption

itoggle caption Courtesy of Susan Tapert/Tim McQueeny/UCSD

Bryce Marcus is a fifth-grader at the KIPP Infinity School in the West Harlem neighborhood of New York City. His curriculum includes emotional development training that teaches him to replace negative thinking with more realistic and flexible thinking. Allison Aubrey/NPR hide caption

itoggle caption Allison Aubrey/NPR

Many schools have made an effort to get rid of unhealthy snacks and educate students about nutrition. Elementary students in Gilbert, Ariz., check out the fruit and vegetable choices as a part of a school lunch program called "A to Z Salad Bar." Tim Hacker/AP/East Valley Tribune hide caption

itoggle caption Tim Hacker/AP/East Valley Tribune

The cornea and lens are responsible for focusing light on the retina. Vision problems are most often the result of an imperfectly shaped eyeball, cornea or lens that prevents light from being properly focused within the eye. National Eye Institute hide caption

itoggle caption National Eye Institute