An urban farmer waters his plants near Bamako, Mali, where the government has set aside nearly 250 acres for market gardens. donkeycart/Flickr hide caption

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A kidney donor is wheeled to an operating room for a transplant at Johns Hopkins Hospital in Baltimore in late June. Brendan Smialowski/AFP/Getty Images hide caption

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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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A rhesus monkey eats watermelon, provided by zookeepers, at the Kamla Nehru Zoological Gardens in India in May 2012. Sam Panthaky/AFP/Getty Images hide caption

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Two men from northwestern Missouri became ill after tick bites infected them with a previously unknown virus. iStockphoto.com hide caption

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