Doctors should use infection control measures if a hospitalized patient has suspected, probable, or confirmed H5N1, putting the patient in an airborne infection isolation room with negative pressure, and using standard, contact, and airborne precautions with eye protection such as goggles or a face shield.

People hospitalized for flu should be tested for bird flu within 24 hours, the U.S. Centers for Disease Control and Prevention said on Thursday, in an expansion of the agency's efforts to tackle increasing infections in humans.

CDC officials say they extended the guidance now because they are seeing more H5N1 patients whose illness they cannot track back to an infected bird or cow.