The year in medicine from A to Z.

Hoping to sharply cut HIV/AIDS transmission rates in the U.S., the Centers for Disease Control and Prevention (CDC) took the unusual step of recommending that doctors ask all patients from ages 13 to 64 whether they want to be tested for the virus. One in four Americans living with HIV don't know they are infected; for them, early diagnosis could mean early treatment and longer lives. Antiretroviral drug therapy has already saved nearly 3 million years of life in the U.S. alone. Meanwhile, the number of people living with HIV/AIDS around the world continues to grow, to 40 million, according to estimates released last week by the U.N.