Global Health

Mosquitoes like this one can carry the virus that causes dengue fever, which may become a bigger problem in some regions as biodiversity is lost. James Gathany/CDC Public Health Image Library hide caption

A health official culls chickens on a poultry farm in a village on the outskirts of Katmandu, Nepal. Chickens suspected of being infected with H5N1 bird flu were found in the area in October. Prakash Mathema/AFP/Getty Images hide caption

Average life expectancy around the world has ticked up over the past twenty years. Here it's shown for men in 2009. The extremes are in dark green and dark red, which represent 78 to 82 years old and less than 66 years old, respectively. Courtesy of the Institute for Health Metrics and Evaluation hide caption

Routine autopsies have become less common in the U.S. But in the past century, post-mortems helped doctors discover many new diseases. iStockphoto.com hide caption

Clostridium difficile bacteria produce a toxin that damages the intestine and causes severe diarrhea. Courtesy of David Goudling/Nature Genetics. hide caption

A boy works at an illegal gold mine in northern Nigeria. Lead from these mines has sickened thousands of children in the region. David Gilkey/NPR hide caption

A child is inoculated with the polio vaccine at a traffic checkpoint just outside Pakistan's capital, Islamabad. Roadside vaccinations help health workers reach children in mobile populations. Jackie Northam/NPR hide caption

Coronaviruses can cause a mild cold or severe pneumonia-like symptoms. Dr. Gopal Murti/Visuals Unlimited/Corbis hide caption

An artistic model of a coronavirus infecting a cell. The family of viruses can cause mild infections, like the common cold, and severe pneumonia-like infections, such as SARS. Peter Kohama/MCT/Landov hide caption