Dr. Nayna Patel performs an ultrasound exam on Rinku Macwan, at a hospital near Ahmedabad, India. It's illegal in India for doctors to reveal a baby's sex during these exams, but many do it anyway. Sam Panthaky/AFP/Getty Images hide caption

itoggle caption Sam Panthaky/AFP/Getty Images

A young boy plays on a commode during an event for World Toilet Day in New Delhi in November. An estimated 131 million Indian homes don't have a latrine or a clean toilet. Raveendran/AFP/Getty Images hide caption

itoggle caption Raveendran/AFP/Getty Images

About a third of the world's population is thought to be infected with Mycobacterium tuberculosis, but only a small fraction of people get the disease. NIAID_Flickr hide caption

itoggle caption NIAID_Flickr

If you catch dengue fever in the Western Hemisphere, it most likely came from the Aedes aegypti mosquito. Muhammad Mahdi Karim /Wikimedia.org hide caption

itoggle caption Muhammad Mahdi Karim /Wikimedia.org

A Palestinian dialysis patient is treated at the Shifa hospital in Gaza City in 2010. Many kidney patients in Gaza struggle to get proper dialysis therapy because machines are often overbooked. Khalil Hamra/AP hide caption

itoggle caption Khalil Hamra/AP

Although tuberculosis is declining around the world, drug-resistant strains of Mycobacterium tuberculosis are on the rise. NIAID/Flickr.com hide caption

itoggle caption NIAID/Flickr.com

The U.S. ranks first in the world at stopping brain cancers, epidemiologists reported Monday. Here neurosurgeon Dr. Roger Hudgins and his assistant, Holly Zeller of Akron, Ohio, look at an MRI scan before performing surgery to remove a brain tumor. Mike Cardew/MCT /Landov hide caption

itoggle caption Mike Cardew/MCT /Landov

By taking antiretroviral drugs during pregnancy, this Tanzanian mother lowered the risk of passing HIV to her daughter. Siegfried Modola/AFP/Getty Images hide caption

itoggle caption Siegfried Modola/AFP/Getty Images

Many homes that were rebuilt after the earthquake in 2010 are even more dangerous than the original ones. This three-story home was put up after the quake but is already slated for demolition to make way for an 18-unit housing project. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

Partnerships instead of short-term help: Jean Jumeau Batsch, an obstetrician-gynecologist in Port-au-Prince, Haiti, is collaborating with Dr. Ambereen Sleemi, from New York City, to build a training program for Haitian OB-GYNs. Courtesy of Dr. Ambereen Sleemi. hide caption

itoggle caption Courtesy of Dr. Ambereen Sleemi.

As an armchair disease detective, you don't have to bother with mundane tasks, like culturing fluorescent bacteria or interviewing the ill. Centers for Disease Control and Prevention hide caption

itoggle caption Centers for Disease Control and Prevention

HIV drugs not only can keep patients healthy but also can stop the sexual transmission of the virus. Here an HIV-positive mother picks up medications at a hospital outside Johannesburg, South Africa. Alexander Joe/AFP/Getty Images hide caption

itoggle caption Alexander Joe/AFP/Getty Images