Eric Goosby, United States Global AIDS coordinator, says field testing is necessary and urgent to determine if HIV testing-and-treating services are feasible. Brendan Hoffman/Getty Images hide caption

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A Haitian protester in Port-au-Prince last month spray-paints a wall, equating the UN mission in Haiti (abbreviated here as MINISTA) with cholera.

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A mother held her baby as she received an experimental malaria vaccine at the Walter Reed Project Research Center in Kombewa in Western Kenya in Oct. 2009.

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Afghan men wait to receive psychiatric treatment in a Kabul hospital. Scarred by decades of war, social problems and poverty, more than 60 percent of Afghans suffer from stress disorders and mental health problems.

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A nurse vaccinates a child against pneumonia at a healthcare center in Managua in January. Nicaragua received pneumococcal vaccines from the GAVI Alliance. ELMER MARTINEZ/AFP/Getty Images hide caption

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A man readies a cow for the International Highland Cattle Show in Glasgow, Scotland. Researchers say genetics and the amount of time animals and humans spend together can affect how viruses spread between species. Jeff J Mitchell/Getty Images hide caption

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Laurence Fishburne as Dr. Ellis Cheever and Kate Winslet as Dr. Erin Mears in the thriller Contagion. Winslet's character was modeled on CDC epidemiologist Dr. Anne Schuchat. Claudette Barius/Warner Bro. Pictures hide caption

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Researchers hope to keep the mosquito that transmits dengue, Aedes aegypti, from infecting humans using the Wolbachia bacterium. James Gathany/CDC Public Health Image Library hide caption

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Women hold mosquito nets after receiving them at a distribution point in Sesheke, Zambia. Researchers say malaria may have rebounded in some parts of Zambia and Senegal because of resistance to the insecticide-treated nets. ASSOCIATED PRESS 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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