(Reuters) -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 ongoing infections in humans.

The Centers for Disease Control and Prevention says hospitals treating people for the flu should test them for avian influenza within 24 hours.

A child ill with fever and conjunctivitis in San Francisco tested positive for bird flu but had no known source of transmission.

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.