A Pakistani man wheels Jamshid, an 8-year-old girl with polio, around the outskirts of the capital Islamabad last July. Behrouz Mehri/AFP/Getty Images hide caption

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The Anopheles stephensi mosquito transmits the malarial parasite while dining on human blood. You can find this type of mosquito in Afghanistan, China, India, Thailand and the Middle East. CDC hide caption

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A mother and child wait to receive treatment at the HIV clinic in Nyagasambu, Rwanda, in Feb. 2008. The clinic was built by the Washington-based Elizabeth Glaser Pediatric AIDS Foundation with a grant from the PEPFAR program. Shashank Bengali/MCT/Landov hide caption

itoggle caption Shashank Bengali/MCT/Landov

Here goes nothing. A big jump over the Zambezi River in Africa. James Whatley/Flickr hide caption

itoggle caption James Whatley/Flickr

U.S. Secretary of Health and Human Services Kathleen Sebelius (center) talks to a health worker during a visit to Eliazar Germain hospital in Port-au-Prince, Haiti, on Monday. It's Sebelius' first visit to the country. Ramon Espinosa/AP hide caption

itoggle caption Ramon Espinosa/AP

Rice farmer Alexi Rochnel shows his blank cholera vaccination card. April is the beginning of Haiti's rainy season, which will likely intensify Haiti's cholera outbreak. John W. Poole/NPR hide caption

itoggle caption John W. Poole/NPR

A makeshift latrine hangs over the water at the edge of Cite de Dieu, a slum in Port-au-Prince, Haiti. John W. Poole / NPR hide caption

itoggle caption John W. Poole / NPR

Rice farmer Alexi Rochnel shows his blank cholera vaccination card. April is the beginning of Haiti's rainy season, which will likely intensify Haiti's cholera outbreak. John W. Poole / NPR hide caption

itoggle caption John W. Poole / NPR

Marlene Lucien controls the hose that fills people's plastic buckets on one busy street corner in Port-au-Prince, Haiti. John Poole/NPR hide caption

itoggle caption John Poole/NPR

A young girl bathes in an irrigation canal. The canal and nearby river are the primary sources of water for most people who live in the country around Saint-Marc, Haiti. John W. Poole/NPR hide caption

itoggle caption John W. Poole/NPR

A health worker injects a woman with a shot of Depo Provera, a quarterly contraceptive injection, at a health clinic in Busia, Uganda, in 2009. MCT/MCT via Getty Images hide caption

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Chhay Meth, 9, suffering through an attack of malaria at the family's home in O'treng village on the outskirts of Pailin, Cambodia, in 2009. A drug-resistant form of malaria in the region medical led officials to declare a health emergency. David Longstreath/AP hide caption

itoggle caption David Longstreath/AP

An artist on Rio de Janeiro's Copacabana beach puts the final touches on a sand sculpture of the assassin bug, which spreads Chagas disease. The sculpture was part of an event in 2009 commemorating the 100th anniversary of the discovery of the disease. Vanderlei Almeida/AFP/Getty Images hide caption

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