The United States has reported its first outbreak of H5N9 bird flu on a duck farm in California, according to the World Organization for Animal Health (WOAH) on Monday.
Why It Matters
H5N9 is a rare subtype of the influenza A virus that can cause highly pathogenic avian influenza (HPAI), also known as bird flu. It's a reassortment strain that originated from the H5N1, H7N9, and H9N2 subtypes.
Additionally, U.S. authorities identified the more common H5N1 strain on the same farm in Merced County, California. In a report to the Paris-based WOAH, officials noted that nearly 119,000 birds on the farm had been culled by December 2.
Newsweek has reached out to the U.S. Department of Agriculture (USDA) and the Centers for Disease Control and Prevention (CDC) for comment on the potential implications of this discovery.
What To Know
The H5N9 strain, a subtype of the influenza A virus, is considered rare. According to the U.S. National Library of Medicine, it is a reassortant virus combining elements from H5N1, H7N9, and H9N2 subtypes. Scientists are studying whether this strain could potentially infect humans or lead to a pandemic.
Federal and state animal health officials, in collaboration with the USDA Animal and Plant Health Inspection Service (APHIS), have begun an epidemiological investigation and enhanced surveillance efforts. Globally, bird flu has prompted the culling of hundreds of millions of poultry since 2022, and its economic impact continues to grow.
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The CDC reports that avian influenza has spread to dozens of mammalian species and led to human cases in the United States, including a death in Louisiana earlier this year. Despite these concerns, the CDC has stated that the current risk to public health remains low.
A newly released map from Newsweek, leveraging data from the U.S. Department of Agriculture (USDA), sheds light on the extent of bird flu outbreaks in poultry flocks across the country since 2022.
What People Are Saying
The U.S. Department of Agriculture said in the report to the WOAH: "The USDA Animal and Plant Health Inspection Service (APHIS), in conjunction with State Animal Health and Wildlife Officials, are conducting comprehensive epidemiological investigations and enhanced surveillance in response to the HPAI related events."
The US National Library of Medicine warns on its website: "Whether this novel H5N9 virus will cause human infections from its avian host and become a pandemic subtype is not known yet."
What Happens Next
Authorities will continue enhanced surveillance and containment efforts in Merced County and neighboring regions. Investigations into the origin and potential spread of the H5N9 strain are ongoing. The CDC, USDA, and international health agencies will monitor for any signs of human transmission while preparing response protocols in case of broader outbreaks.
Update 01/27/25 2:31 p.m. ET: This article was updated with additional information.
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About the writer
Gabe Whisnant is Deputy Weekend Editor at Newsweek based in South Carolina. Prior to joining Newsweek in 2023, he directed ... Read more