HIV infection: HIV screening
The test: Usually a blood test to detect antibodies to the virus.
The guidelines: In 2006 the U.S. Centers for Disease Control and Prevention recommended that everyone ages 13 to 64 be screened for HIV infection, regardless of their risk profile. The task force concluded there is insufficient evidence to recommend universal screening, though it does urge testing for people at high risk for HIV because of sexual history, history of injection-drug use or history of blood transfusions.
What to consider: More than 1 million Americans are infected with the HIV virus, and about one in five don't know it. That means they don't get effective treatments, which helps promote a new wave of infections each year — more than 56,000 in 2008. About 15 percent of new infections that year were among people age 50 and older. According to John G. Bartlett, M.D., an HIV specialist at the Johns Hopkins University School of Medicine, the main area where people tend to underestimate their risk is sexual transmission, a risk that includes exposure to a partner's contacts.
Katharine Greider lives in New York and writes about health and medicine.