Originally published by our sister publication Infectious Disease Special Edition
By Marie Rosenthal, MS
The CDC has confirmed a human infection with avian influenza A(H5N1) in a California child—the first reported pediatric avian influenza H5 virus infection in the United States.
Consistent with previously identified human cases in the United States, the child experienced mild symptoms and received antivirals for inflluenza. 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. The California Department of Public Health (CDPH) is investigating into the child’s possible source of H5N1 exposure.
During CDPH’s investigation, all household members reported having symptoms, and specimens were collected from these people. All test results from household members were negative for H5 avian flu, and some family members were positive for the same common respiratory viruses as the child. Contact tracing continues, but currently there is no evidence of person-to-person spread of H5N1 avian flu from this child to others, according to the CDC. To date, there has been no person-to-person spread identified associated with any of the H5N1 bird flu cases reported in the United States.
This pediatric case was detected through influenza testing and reported to CDPH through influenza surveillance. This is the second U.S. case identified through national surveillance. The CDC continues to closely monitor available data from influenza surveillance systems, particularly in states affected by outbreaks in animals, including California, where widespread outbreaks of H5N1 bird flu have been detected in wild birds and domestic poultry since 2022, and dairy herds since August 2024, in that state.
Limited and sporadic human infections with avian influenza H5N1 virus, where animal exposure was not identified, are uncommon but have occurred, primarily in countries other than the United States. These instances underscore the importance of ongoing surveillance and investigations at the local, state and federal levels, according to the CDC.
Including this most recent case, 55 human cases of H5 bird flu have now been reported in the United States during 2024, with 29 in California.
In related news, Canada also reported a case of pediaric H5 avian flu in a teenager from British Columbia, who was hospitalized and tested. The Public Health Agency of Canada's National Microbiology Laboratory (NML) in Winnipeg confirmed that the individual has avian influenza H5N1 and the genomic sequencing result indicates that the virus is related to the avian influenza H5N1 viruses from the ongoing outbreak in poultry in British Columbia (Influenza A [H5N1], clade 2.3.4.4b, genotype D1.1).
As is the case in the American child, officials do not yet know how the teenager became infected but are conducting a trace-back investigation.
“This detection was picked up via hospital-based influenza surveillance, confirming that human influenza surveillance in British Columbia and Canada is effective at detecting avian influenza A(H5). We must continue to remain vigilant in our efforts to prevent the spread of avian influenza between animals and to humans," said Theresa Tam, MD, the Chief Public Health Officer of Canada.
As a general precaution to prevent avian influenza infections, advise patients not to handle live or dead wild birds or other wild animals, and keep pets away from sick or dead animals. People who work with sick animals or in contaminated environments, such as farmers, should take precautions, including using personal protective measures to reduce the risk for avian influenza.