"This is the first reported avian influenza H5 virus infection in a child in the United States," CDC said in a statement.

The case was reported from California.

Consistent with previously identified human cases in the United States, the child reportedly experienced mild symptoms and received flu antivirals, US CDC said.

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.

US CDC said 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.

"During CDPH's investigation, all household members reported having symptoms and specimens were collected from those people. All test results from members of the household were negative for H5 bird flu, and some family members were positive for the same common respiratory viruses as the child," the statement said.

"Contact tracing continues, but there is currently no evidence of person-to-person spread of H5N1 bird flu from this child to others," the statement said.

CDC said there has been no person-to-person spread identified associated with any of the H5N1 bird flu cases reported in the United States.