The disease, which can be treated if diagnosed quickly, has hit particularly hard in the Americas, where the number of cases increased from 66,000 in 1980 to 552,000 in 2006, according to the Pan American Health Organization.

Photograph by Bryan Reynolds/Getty Images

EMAIL NEWSLETTER Photos and News of the Week Get the top photos and news of the week from National Geographic News, plus occasional breaking-news alerts. See Sample >> Please enter a valid email address Thank You! Subscription accepted. An email confirmation will be sent. Privacy Policy MOST VIEWED NEWS Hurricane Gustav to Become Gulf Coast Monster? Ancient Amazon Cities Found; Were Vast Urban Network Hurricane Gustav: Complete Coverage NEWS FEEDS      Get our news delivered directly to your desktop—free. How to Use XML or RSS