Shoppers check out vodka in a street kiosk in Moscow in 2008. Alexander Nemenov/Getty Images hide caption

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Palestinian girls read the Koran at a camp in Gaza City, June 2012. In poor countries, boys are 20 percent more likely than girls to enroll in school, UNICEF says. Mahmud Hams/AFP/Getty Images hide caption

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Graduate student Jennifer Klunk of McMaster University examines a tooth used to decode the genome of the ancient plague. Courtesy of McMaster University hide caption

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A vendor sells chickens at the Kowloon City Market in Hong Kong last month. As a precautionary measure against the deadly H7N9 virus, Hong Kong has temporarily stopped importing poultry from mainland farms. Lam Yik Fei/Getty Images hide caption

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Young boys suspected of having Guinea worm infections wait for the parasite to emerge through the skin at a clinic in South Sudan. Louise Gubb/The Carter Center hide caption

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The U.K. has plenty of fresh produce available, such as these vegetables on display at a garden show in Southport, England. But these healthy options cost more in the U.K. than in any other country in Western Europe. Christopher Furlong/Getty Images hide caption

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Tobacco companies incorporated doctors in their ads, such as this 1930 Lucky Strike campaign, to convince the public that smoking wasn't harmful. Stanford University hide caption

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Neonatal nurse Florence Mwenifumbo monitors a newborn receiving bubble CPAP treatment in Blantyre, Malawi. The device was developed by students at Rice University in Houston. Rice 360/Rice University hide caption

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Government workers exercise at their office in Mexico City, August 2013. To counter the obesity epidemic, the city requires all government employees to do at least 20 minutes of exercise each day. Tomas Bravo/Reuters /Landov hide caption

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Yonta, 6, rests with her brother Leakhena, 4 months, under a mosquito bed net in the Pailin province of Cambodia, where deaths from malaria have decreased sharply in the past two decades. Paula Bronstein/Getty Images hide caption

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Almaz Acha sits with her baby Alentse at her home in the rural community of Sadoye, in southern Ethiopia. Families in rural communities, like this one, have benefited from Ethiopia's health extension program. Julien Behal/PA Photos /Landov hide caption

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The skull of a female Neanderthal, who lived about 50,000 years ago, is displayed at the Natural History Museum in London. Rick Findler/Barcroft Media/Landov hide caption

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When Benta Odeny was diagnosed with HIV, she started to protect her husband Daniel from the virus by taking antiretroviral medications. The same drugs also helped her give birth to an HIV-negative daughter, Angelia. Gregory Warner/NPR hide caption

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