Ramon Maldonado-Cardenas grimaces as he gets a flu shot from pharmacy student Khoa Truong during a health fair in Sacramento, Calif., last October. Rich Pedroncelli/AP hide caption

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Old paint is the chief source of lead poisoning in children. iStockphoto.com hide caption

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H5N1 avian flu viruses (seen in gold) grow inside canine kidney cells (seen in green). Cynthia Goldsmith/CDC hide caption

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Connor Perruccello-McClellan, a senior at Providence Country Day School in Rhode Island, has been vaccinated against HPV, something less than 1 percent of U.S. males can say. Richard Knox/NPR hide caption

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