A doctor examines chest X-rays at a tuberculosis clinic in Gugulethu, Cape Town, South Africa in late 2007. The number of TB cases that don't respond to both first- and second-line medications is rising worldwide. Karin Schermbrucker /AP hide caption

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Families wait for hours to register at the Yida refugee camp in South Sudan along the northern border in early July. Within a few weeks, the population of the camp more than doubled, leading to shortages of food, water and medicine. Paula Bronstein/Getty Images hide caption

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Thousands of doses of cholera vaccine sit in a refrigerated trailer in a United Nations compound in Saint-Marc, Haiti, in March. After some delays, a vaccination project proved successful. John Poole/NPR hide caption

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A man smokes a bidi on "No Tobacco Day," May 31, in Allahabad, India. These small, hand-rolled cigarettes are popular in India and Bangladesh because they are far cheaper than regular cigarettes. Rajesh Kumar/AP hide caption

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Vampire bats are common in Central and South America, where they feed on livestock and sometimes people. Michael & Patricia Fogden/Corbis hide caption

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The Ebola virus causes a deadly form of hemorrhagic fever. Frederick Murphy/CDC hide caption

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"You've been condomized!" said Joy Lynn Alegarbes, of The Condom Project, which promoted safe sex at the 19th International AIDS Conference. The group handed out more than 850,000 condoms this week. Benjamin Morris/NPR hide caption

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Anti-AIDS posters at the Eshowe public health clinic in Kwazulu Natal, South Africa. Clinicians there are hoping to slow the spread of HIV by getting more people treatment. Jason Beaubien /NPR hide caption

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A 3-D model of HIV peeled back to show its layers. HIV's genetic material sits inside a spherical shell (gray matrix) studded with spikes (dark gray and orange). The sphere pops open when a T cell tugs on a spike. Courtesy of Ivan Konstantinov/© Visual Science 2011 hide caption

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Researchers with HIV medication at a public research lab at the Oswaldo Cruz Foundation, or Fiocruz, in Rio de Janeiro. Jason Beaubien/NPR hide caption

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HIV Prevention Drug Truvada No Quick Fix For Brazil's Epidemic

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A lone pig roots through trash dumped over the side of a sewage canal that runs from the center of Port au Prince through Cite de Dieu. During the rainy season, the canal overflows its banks and fills nearby houses with sewage, which can carry cholera. John W. Poole /NPR hide caption

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