Dorothy Mwesiga with her third child. Mwesiga was treated with antidepressant drugs and talk therapy for her postpartum depression. Joanne Silberner for NPR hide caption

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Indian schoolchildren write English alphabets on slates at a primary school outside Hyderabad in June. India is on track to overtake China as the most populous nation in just 16 years. Noah Seelam/AFP/Getty Images hide caption

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Internally displaced Somalis wait for food at a distribution point at the government-run Badbaado refugee camp in a suburb of the capital Mogadishu on Tuesday. The U.N.'s World Food Programme said its airlift to Mogadishu for drought victims was delayed Tuesday because of last-minute bureaucratic hurdles in Kenya. Mustafa Abdi/AFP/Getty Images hide caption

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An Afghan health worker administers the polio vaccine to a child during a vaccination campaign in Kabul, Afghanistan, in 2010. Majid Saeedi/Getty Images hide caption

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Saruuro Aden traveled on foot from southern Somalia across the Kenyan border with her four children. She says they walked for 10 days. Ofeibea Quist-Arcton/NPR hide caption

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Bottles of antiretroviral drug Truvada, a medicine used in trials that showed a reduction in transmission of HIV between heterosexuals. Justin Sullivan/Getty Images hide caption

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A study of Ugandans found antiretroviral drugs can extend the lifespans of people with HIV to nearly normal lengths. Adek Berry/AFP/Getty Images hide caption

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The trade in dried geckos, such as these from Indonesia, is on the rise amid growing demand for their use as an ingredient in medicinal and skin care products in Asia. Ulet Ifansasti/Getty Images hide caption

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Mourners attend a memorial service for recent cholera victims in Haiti that took place Wednesday in Savanette, an isolated community in the mountains outside Mirebalais, Haiti. Cate Oswald/Partners in Health hide caption

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Bottles of antiretroviral drug Truvada, a medicine used in trials that showed a reduction in transmission of HIV between heterosexuals. Justin Sullivan/Getty Images hide caption

itoggle caption Justin Sullivan/Getty Images

Lucrecia Silva and her daughter, Helena, are both HIV-positive. They wait as a nurse in Macia writes a prescription for Helena's anti-retroviral drugs. Andrea Hsu/NPR hide caption

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