San Juan Creek meets the Pacific Ocean at Doheny State Beach in Dana Point, Calif. The poor water quality off Doheny State Beach put in a list of worst beaches in the U.S. Reed Saxon/AP hide caption

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Cambodian women wear masks as they walk in a market in Phnom Penh in Oct. 2009. That month a second Cambodian died from swine flu, health officials said. Tang Chhin Sothy/AFP/Getty Images hide caption

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Pretty to look at, almost, but Klebsiella pneumoniae bacteria these are a common cause of infections in hospitals. CDC hide caption

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Vietnam has contained the fatal bird flu cases that raged in the late 2000s, but it is still struggling with new cases of the virulent disease. Here, a poultry trader loads live chickens onto his motorbike on March 16 at a market outside Hanoi. Hoang Dinh Ham/AFP/Getty Images hide caption

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A Haitian protester in Port-au-Prince last year spray-paints a wall, equating the UN mission in Haiti (abbreviated here as MINISTA) with cholera. Thony Belizaire/AFP/Getty Images hide caption

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Timothy Ray Brown, widely known in research circles as the Berlin patient, was cured of his HIV infection by bone marrow transplants. Now scientists are trying to make sense of the traces of HIV they've found in some cells of his body. Richard Knox/NPR hide caption

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A nurse in Washington administers the whooping cough vaccine to a child in May. In response to the epidemic, more than 82,000 adults have also received the vaccine this year. Ted S. Warren/AP hide caption

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Gao Weiwei, a doctor of the Beijing Chest Hospital which specializes in the treatment of tuberculosis, talks to a patient suspected to have tuberculosis at the hospital in Tongzhou, near Beijing, March 27, 2009. Ng Han Guan/AP hide caption

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A Pakistani man wheels Jamshid, an 8-year-old girl with polio, around the outskirts of the capital Islamabad last July. Behrouz Mehri/AFP/Getty Images hide caption

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The Anopheles stephensi mosquito transmits the malarial parasite while dining on human blood. You can find this type of mosquito in Afghanistan, China, India, Thailand and the Middle East. CDC hide caption

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