The U.S. Centers for Disease Control and Prevention on Thursday urged clinicians and laboratories to test for the variant of influenza A virus in patients ideally within 24 hours of hospitalization, as part of its efforts to tackle the ongoing sporadic human infections with bird flu.

The CDC has confirmed a positive bird flu case in a child in San Francisco, the second juvenile case of H5N1 in the country.

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.