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.

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.

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

As the Centers for Disease Control and Prevention (CDC) explains, bird flu is a disease caused by the influenza A virus. At the same time, recent CDC data shows that seasonal influenza A is rising across the U.

Public health officials have confirmed a San Francisco child is the second pediatric case of bird flu in the U.S. According to the CDC, no additional cases have been identified among the child's contacts.