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

The U.S. Centers for Disease Control and Prevention on Thursday urged clinicians and laboratories to test for the bird flu within 24 hours in people hospitalized with influenza, as part of its efforts to tackle the ongoing 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.

The CDC is calling for expanded testing of bird flu after a child in California tested positive for the virus despite no known contact with animals.