An health official wearing protective gear culls a bird at a poultry farm after a naturally occurring bird flu virus was detected near Agartala, India, in January. Sushanta Das/AP hide caption

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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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Nurse Susan Peel gives a whooping cough vaccination to a student at Inderkum High School in Sacramento, Calif., in 2011. Now it seems likely such shots will become routine for senior citizens, too. Rich Pedroncelli/AP 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

itoggle caption Cynthia Goldsmith/CDC

Virologists and other scientists are meeting at the World Health Organization's Geneva headquarters to talk about the bird flu. Pierre Virot/WHO hide caption

itoggle caption Pierre Virot/WHO

Students at a University of London class in Mexico City wear masks to protect them against swine flu in May 2009. High schools and universities closed by the pandemic had just reopened across Mexico. Brennan Linsley/AP hide caption

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Inattention to catheters used often in ICUs can lead to serious infections. 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

itoggle caption Cynthia Goldsmith/CDC

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

itoggle caption David Longstreath/AP

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

itoggle caption Vanderlei Almeida/AFP/Getty Images