A mobile clinic set up to test students for HIV is parked near Madwaleni High School in Mtubatuba, KwaZulu-Natal, South Africa on March 8, 2011. Parts of the South African province have HIV rates that are more than twice the national average. Stephane de Sakutin/AFP/Getty Images hide caption

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Health care workers in South Africa speak to residents during a door-to-door AIDS awareness campaign, part of a series of prevention efforts that has helped lower the country's HIV infection rate. Mujahid Safodien /Reuters /Landov hide caption

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

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Drag queens at an outdoor restaurant in Copacabana incorporate safe sex messages into a show of lip-synced songs and risque jokes. Jason Beaubien/NPR hide caption

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Longtime AIDS activist Dr. Ashraf Grimwood says South Africa has made huge strides in confronting HIV. But he worries that giving anti-retroviral drugs to healthy people could have negative consequences in the long term. Jason Beaubien/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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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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A boy waits to get his anti-AIDS drugs from pharmacist Rajesh Chandra at the Botswana-Baylor Children's Clinical Center of Excellence in Gaborone. Jason Beaubien/NPR hide caption

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Johane Setlhare began taking anti-AIDS drugs, provided by the government, in 2007. Two years later, he regained enough strength to build the house that's behind him. Jason Beaubien/NPR hide caption

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A local organization is trying to curb HIV transmission rates among gay men in Kisumu, Kenya. eduardoavila/Flickr hide caption

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Joseph Ochieng, 18, gets circumcised at the Siaya General Hospital in western Kenya. Jason Beaubien/NPR hide caption

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In heavily polluted Mexico City, crime writer Paco Ignacio Taibo II describes his exhausted detective Hector Belascoaran Shayne as looking out at his hometown and seeing "a city that was trying to hide itself in the smog." Ronaldo Schemidt/AFP/Getty Images hide caption

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Tourists visit the San Felipe neighborhood in Panama City in December 2011. Panama is experiencing record economic growth, but many fear the benefits aren't trickling down to the poor. Rodrigo Arangua/AFP/Getty Images hide caption

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The Panama Canal is undergoing its biggest overhaul since it was opened nearly a century ago. A third channel is being built, which will allow more and larger ships to pass through. Arnulfo Franco/AP hide caption

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