The Centers for Disease Control and Prevention (CDC) has confirmed a human infection with avian influenza A(H5N1) (H5N1 bird flu) in a child in California. This is the first reported avian influenza H5 virus infection in a child in the United States. Consistent with previously identified human cases in the United States, the child reportedly experienced mild symptoms and received flu antivirals. There were low levels of viral material detected in the initial specimen collected, and follow-up testing of the child several days later was negative for H5 bird flu but was positive for other common respiratory viruses. The child is recovering from their illness. An investigation by the California Department of Public Health (CDPH) into the child’s possible H5N1 exposure source is ongoing.