Dengue fever patients are treated in a hospital in Asuncion, Paraguay, in January. Norberto Duarte/AFP/Getty Images hide caption

itoggle caption Norberto Duarte/AFP/Getty Images

The city of Sao Paolo, Brazil, shot with a fisheye lens. Standards of living are improving not just in the big developing nations like Brazil, but also in smaller countries such as Bangladesh and Ghana. Daniel Incandela/Flickr via Wikimedia Commons hide caption

itoggle caption Daniel Incandela/Flickr via Wikimedia Commons

A performer drinks a soda in Ahmedabad, India in 2010. A study found that rising diabetes prevalence in countries like India is strongly tied to sugar consumption. Sam Panthaky/AFP/Getty Images hide caption

itoggle caption Sam Panthaky/AFP/Getty Images

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

itoggle caption James Gathany/CDC Public Health Image Library