A package of K2, a concoction of dried herbs sprayed with chemicals sometimes called synthetic marijuana. New York moved to ban a wide range of products like these this week. Kelley McCall/AP hide caption

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Chhay Meth, 9, suffering through an attack of malaria at the family's home in O'treng village on the outskirts of Pailin, Cambodia, in 2009. A drug-resistant form of malaria in the region medical led officials to declare a health emergency. David Longstreath/AP hide caption

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An artist on Rio de Janeiro's Copacabana beach puts the final touches on a sand sculpture of the assassin bug, which spreads Chagas disease. The sculpture was part of an event in 2009 commemorating the 100th anniversary of the discovery of the disease. Vanderlei Almeida/AFP/Getty Images hide caption

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Experiences in youth shape our health in old age. That's the key lesson from the world's longest-running medical study. iStockphoto.com hide caption

itoggle caption iStockphoto.com