Herpes meds may suppress more than herpes. People with HIV who control their genital herpes cut their danger of passing HIV to partners—and may reduce their own viral loads. Two studies from last February’s Conference on Retroviruses and Opportunistic Infections found that women with herpes and HIV who took herpes meds (acyclovir or valacyclovir) reduced HIV shedding. HIV levels also dropped—in blood as well as in genital secretions.

How did the drugs do it? “A herpes outbreak revs up the immune system, activating CD4 cells in an effort to fight the infection,” says Lloyd Bailey, MD, of New York City’s St. Vincent’s Midtown Hospital. “Activated CD4 cells are available for HIV infection.” Stifling herpes, then, may limit HIV’s chances to attack. If you have HIV, consider being tested for herpes—it doesn’t always cause symptoms.