First Outbreak of H5N9 Bird Flu Reported in U.S. Poultry

What Happened?

The outbreak was identified at a duck farm in Merced County, California, according to a report submitted to the World Organisation for Animal Health (WOAH). Alongside the rarer H5N9 strain, the more common H5N1 variant was also detected on the same farm.

The farm housed approximately 119,000 birds, all of which were culled by December 2, 2024, to contain the spread. The United States Department of Agriculture (USDA) confirmed the H5N9 case, stating this is the first occurrence of this strain in American poultry.

Why It Matters

HPAI strains, including H5N9 and H5N1, have wreaked havoc globally in recent years. These viruses have led to the culling of millions of birds, causing significant losses in poultry industries worldwide.

The impact extends beyond birds. Bird flu strains like H5N1 have crossed species barriers, infecting dozens of mammal species and, in rare cases, humans. A recent death in Louisiana due to H5N1 highlights the potential risks these outbreaks pose to public health.

What’s Being Done?

The USDA’s Animal and Plant Health Inspection Service (APHIS), in collaboration with state officials, is conducting a thorough epidemiological investigation. Enhanced surveillance efforts are underway to prevent further spread.

Authorities are also taking measures to monitor nearby farms and wildlife populations, as these outbreaks can quickly escalate without strict containment efforts.

What Is H5N9?

While H5N9 is less common than H5N1, it is still classified as highly pathogenic. The virus causes severe disease in birds and poses potential risks to humans, though there have been no reported human cases of H5N9 in the U.S. so far.

What’s Next?

The outbreak underscores the importance of vigilance in managing bird flu outbreaks, both for the poultry industry and public health.

• Poultry farms will need to ramp up biosecurity measures to prevent further infections.
• Wildlife monitoring programs are critical, as migratory birds often play a role in spreading these viruses.
• Consumers are unlikely to see immediate effects, but prolonged outbreaks could impact poultry prices and availability.

This incident serves as a reminder of the interconnectedness of animal health, agriculture, and human safety. With comprehensive measures in place, authorities aim to contain this outbreak and prevent further challenges to public health and the economy.