The varicella zoster virus causes chickenpox in children, then lurks in the body for years and can cause painful shingles later in life. James Cavallini/Science Source hide caption

itoggle caption James Cavallini/Science Source

The outbreak of Middle East respiratory syndrome is slowing down in South Korea, but people were still wearing surgical masks around Seoul on Monday. Ed Jones/AFP/Getty Images hide caption

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Raymond Wang, 17, of Vancouver, celebrates winning first place at the Intel International Science and Engineering Fair in Pittsburgh, May 15. Courtesy of Kathy Wolfe/Intel hide caption

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In front of the emergency room at the Samsung Medical Center in Seoul, medical workers care for a man suspected of having the Middle Respiratory syndrome on Monday. Jung Yeon-Je/AFP/Getty Images hide caption

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Of I Wish You the Sunshine of Tomorrow, Rodgers says: "The ICU room my dad was in on the day he died had yellow walls. Every time we visited him we had to wear hospital gowns that were a bright yellow. [It] was a recurring color in that whole time frame of my life." Courtesy of Jennifer Rodgers hide caption

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Health worker Jackie Carnegie delivers a rubella vaccine in Colorado in 1972. Ira Gay Sealy/Denver Post via Getty Images hide caption

itoggle caption Ira Gay Sealy/Denver Post via Getty Images

Rod-shaped specimens of Yersinia pestis, the bacterial cause of plague, find a happy home here in the foregut of a flea. Fleas can transmit the infection to animals and people, who can get pneumonic plague and transmit the infection through a cough or kiss. Science Source hide caption

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Secretary of State John Kerry and African Union Commission Chairperson Nkosazana Dlamini Zuma signed an agreement Monday to establish the first Centers for Disease Control and Prevention in Africa. The U.S. will provide technical advice and a few staff for the agency. Alex Wong/Getty Images hide caption

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Maria Carmen Castro, 46, of Lima, Peru, is a survivor of MDR-TB — multidrug-resistant tuberculosis. Partners In Health treated her and loaned her money to open a small store. "Because of my TB and thanks to God and Partners In Health, now I have my own business," she says. Jason Beaubien/NPR hide caption

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Grey lines connecting health care workers (marked with "+") and patients represent contacts between them. The red figures are carriers of MRSA. Obadia et al./PLOS Computational Biology hide caption

itoggle caption Obadia et al./PLOS Computational Biology

The effects of malaria in the brain are clear: A healthy brain, right, has many grooves and crevices. But when the brain swells up, left, these crevices smooth out. Courtesy of Michigan State University hide caption

itoggle caption Courtesy of Michigan State University

Who, me? The Asian relative of this domestic gerbil is a well-known host to the bacteria that cause plague. Valentina Storti/Flickr hide caption

itoggle caption Valentina Storti/Flickr

The rapid Ebola test from Corgenix Medical Corporation is small and easy to use. But because it involves blood, health workers would still need to run the test at a lab to stay safe. Courtesy of Corgenix Medical Corp. hide caption

itoggle caption Courtesy of Corgenix Medical Corp.