From the caves of South Africa to the CDC headquarters, monitoring the work of virus hunters and disease detectives.

Dr. Gupta sits down with twins Scott and Mark Kelly after Scott's historic mission of spending a year in space to test the physical and mental toughness needed for a mission to Mars.

CNN's Dr. Sanjay Gupta investigates the science behind a new trend where doctors are prescribing video games instead of drugs - training your brain to be stronger, faster, better.