Avian influenza (HPAI) A(H5N1), commonly known as bird flu, has seen an increase in human cases in the United States recently, mainly among poultry and dairy workers. H5N1 has primarily circulated in the Midwest, and these cases are raising concerns about potential human transmission and broader public health implications. Understanding the current landscape of H5N1, including recent data and prevention strategies, is essential as health officials continue to monitor the situation.1
The California Department of Public Health (CDPH) announced today that a child from Alameda County has tested positive for a suspected H5N1 avian flu infection. The child, who displayed mild upper respiratory symptoms, has no known contact with infected animals. If confirmed, this would be the second case in North America involving a child with an undetermined source of infection. It would also be the second such case in the US this year, involving someone with no exposure to sick farm animals. This would also mark the 27th H5N1 case in California this year, and the first not linked to sick animals on dairy or poultry farms.2
The Alameda County child is recovering at home, and health officials are investigating the potential source of the infection. While the child had no known contact with infected animals, the investigation is focusing on possible exposure to wild birds, particularly as the H5N1 virus spreads along migratory bird routes. Alameda County does not have commercial dairy herds, and the child had attended daycare while symptomatic. Health officials have notified other contacts and provided preventive treatment as a precaution.2
The child’s initial test for H5N1 avian flu showed a low-level detection of the virus, suggesting the child was unlikely to be infectious. Follow-up tests conducted four days later came back negative, and further tests indicated the presence of other respiratory viruses, which may have been responsible for the child’s symptoms. Specimens have been sent to the CDC for final confirmation.2
On September 6th, the CDC confirmed a human case of H5N1 avian influenza in Missouri, marking the first instance in which the virus was transmitted to a person without a known exposure to sick or infected poultry or livestock. The patient, who had underlying medical conditions, was hospitalized, treated with antiviral medications, and has since recovered. This case stood out because, unlike previous cases, there was no direct connection to poultry or livestock, raising concerns about potential unknown sources of transmission.3 This case, along with the new case in California, is notable for standing apart from earlier H5N1 cases in 2024, all of which involved individuals with a history of exposure to sick or infected poultry.
Despite concerns about the suspected infection, health authorities have emphasized that no human-to-human transmission of H5N1 avian flu has been documented in over 15 years. The ongoing investigation is focused on identifying the source of exposure, but as of now, there is no evidence of a broader threat to public health. Authorities continue to monitor the situation and take appropriate precautions to prevent further spread.2
What You Need To Know
A child in California has tested positive for a suspected H5N1 infection, marking the second North American case this year with an undetermined source of exposure.
Oregon has confirmed its first human case of H5N1 in an individual linked to a poultry outbreak with mild symptoms and no evidence of person-to-person transmission.
Canada has reported its first locally acquired H5N1 infection in a critically ill teenager, marking a development amid rising poultry outbreaks in the region.
First Human Case in Oregon
Oregon has confirmed its first human case of H5N1 in a person linked to a poultry outbreak in Clackamas County. The individual, who experienced mild illness and has since recovered, had close exposure to infected birds. Health officials report no evidence of person-to-person transmission, and the public risk remains low.4
First Human Case in Canada
Just last week, Canadian health officials reported a critically ill teen from British Columbia who was hospitalized with an H5N1 infection, marking the first case of its kind in North America. The Public Health Agency of Canada confirmed that the H5N1 virus detected in the teen was closely related to strains circulating in local poultry. Genetic sequencing identified the virus as part of the 2.3.4.4b clade and D.1.1 genotype.5
This follows an uptick in poultry outbreaks across Western Canada and several US states, likely due to the migration of infected birds along the Pacific flyway. As of now, no other human infections have been reported in Canada.5
References
2. State Reports Single, Possible Case of Bird Flu Virus in Child with Mild Symptoms. The California Department of Public Health. November 19, 2024. Accessed November 20, 2024. https://www.cdph.ca.gov/Programs/OPA/Pages/NR24-037.aspx
4. News Release. Oregon confirms first human case of highly pathogenic avian influenza. Oregon Health Authority. November 15, 2024. Accessed November 20, 2024. https://content.govdelivery.com/accounts/ORHA/bulletins/3c21d2e
