Before using direct-acting antivirals to treat patients with chronic hepatitis C, health care professionals should screen the patients for evidence of current or prior hepatitis B, the Food and Drug Administration said in a safety alert yesterday. FDA has identified 24 cases of hepatitis B reactivation in co-infected patients treated with direct-acting antivirals in the past three years. Two of the patients died and one required a liver transplant. As a result, the agency is requiring drug labels for these medications to include a prominent warning about the risk of hepatitis B reactivation.