United Nations Aids Executive Director Michel Sibide hugs Secretary of State Hillary Clinton after they they presented the a road map for stopping HIV around the world. Jim Watson/AFP/Getty Images hide caption

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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

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Students paste red ribbons on a window to mark World AIDS Day in Nanjing, China, in 2006. Between 2007 and 2011, the number of newly diagnosed HIV cases in China has nearly quadrupled to 40,000. AP hide caption

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A controversial pilot project reduced the cost of the most effective malaria drugs by giving manufacturers, such as Guilin Pharmaceutical in China, subsidies. Frederic J. Brown/AFP/Getty Images hide caption

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Health workers take a blood sample from an infant to test for the malaria at a clinic along the border between Thailand and Myanmar. Ben de la Cruz/NPR hide caption

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A health worker in Pakistan marks a child's finger with ink after giving him the polio vaccine. Jackie Northam/NPR hide caption

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As white-tailed deer have returned to New England in the past century, they've brought with them tick-borne parasites that cause human diseases. marcinplaza /iStockphoto.com hide caption

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A mother dresses her baby after doctors examined him during the malaria vaccine trial at the Walter Reed Project Research Center in Kombewa in Western Kenya in October 2009. Karel Prinsloo/AP hide caption

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This 5-year-old boy was carried to a Thai malaria clinic by his mother from deep inside Myanmar. If the mother had waited even a day longer, doctors say, the child probably would have died. Ben de la Cruz/NPR hide caption

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Ado Ibrahim carries his son Aminu through a village in northern Nigeria. Aminu, 4, was paralyzed by polio in August. David Gilkey/NPR hide caption

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Daw Khin Twon, an undocumented immigrant from Burma, rests at home after receiving malaria treatment at the Mae Tao Clinic in Mae Sot, Thailand. Ben de la Cruz/NPR hide caption

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Blood samples dry during malaria screening. Public health workers call for more malaria testing in Africa to stop costly drugs from being handed out to kids with pneumonia. Paula Bronstein/Getty Images hide caption

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Hurricane Sandy's tear across the Caribbean left at least 54 dead in Haiti, where many people still live in tents because of damage from the 2010 earthquake. Thony Belizaire/AFP/Getty Images hide caption

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