About a third of the world's population is thought to be infected with Mycobacterium tuberculosis, but only a small fraction of people get the disease. NIAID_Flickr hide caption

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Although tuberculosis is declining around the world, drug-resistant strains of Mycobacterium tuberculosis are on the rise. NIAID/Flickr.com hide caption

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Klebsiella pneumoniae, seen here with an electron microscope, are the most common superbugs causing highly drug-resistant infections in hospitals. Kwangshin Kim/Science Source hide caption

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Infections With 'Nightmare Bacteria' Are On The Rise In U.S. Hospitals

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A new coronavirus looks a lot like its cousin SARS under the microscope, but it appears they're quite different when it comes to contagiousness. NIAID/RML hide caption

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Health officials around the world are on constant lookout for the deadly bird flu. Here a worker collects chickens on a farm in Kathamndu, Nepal, where the virus was suspected of infecting poultry last October. Prakas Mathema/AFP/Getty Images hide caption

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Feds Set New Rules For Controversial Bird Flu Research

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Coronaviruses have a characteristic crown of tentacles when viewed under the electron microscope. BSIP/UIG via Getty Images hide caption

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Virologists discovered the new coronavirus after it killed a Saudi Arabian man last summer. Elizabeth R. Fischer/Rocky Mountain Labs/NIAID/NIH 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 kissing 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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Health workers in Nepal culled chickens and destroyed eggs following an outbreak of bird flu in Kathmandu in October 2012. Prakash Mathema/AFP/Getty Images hide caption

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Scientists Put An End To Moratorium On Bird Flu Research

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A boy with multiple Guinea worms sits outside a containment center in northern Ghana, February 2007. Wes Pope/Chicago Tribune/MCT /Landov hide caption

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When flu viruses (in red) accumulate an escape protein too quickly, they exit the cell nucleus (in blue) before they've made enough viral copies to spread the infection. Benjamin tenOever hide caption

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A copper engraving from 1656 shows a plague doctor in Rome wearing a protective suit and a mask. Artwork by Paul Furst /Wikimedia.org hide caption

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Microbiologist Emma Allen-Vercoe invented the Robogut, a mechanical device that mimics conditions in the human colon. Courtesy of thestar.com hide caption

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