Rare H5N9 Bird Flu Detected at California Duck Farm

Duck farm bird flu outbreak California
Ducks on a duck farm. Photo by Niklas Hamann on Unsplash

In a significant development, the United States has reported its first outbreak of the H5N9 avian influenza strain at a duck farm in Merced County, California. This marks the inaugural detection of this particular strain in U.S. poultry.

The U.S. Department of Agriculture (USDA) confirmed the presence of the highly pathogenic avian influenza (HPAI) H5N9 strain at the affected farm. Notably, this facility had previously encountered the more prevalent H5N1 strain, leading to the death of nearly 119,000 birds by December 2, 2024, Reuters reported.

The USDA, in collaboration with state animal health and wildlife officials, has initiated comprehensive epidemiological investigations and heightened surveillance measures in response to this outbreak. The primary objectives are to determine the origin of the virus, assess its spread, and implement strategies to prevent further transmission.

“This is the first confirmed case of HPAI H5N9 in poultry in the United States,” the U.S. Department of Agriculture said in the report to the World Organization for Animal Health, as Reuters reported. “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,” it added.

The emergence of the H5N9 strain is particularly concerning due to its rarity and potential implications for both animal and human health. While the H5N1 strain has been the dominant variant in recent outbreaks, the detection of H5N9 introduces new challenges for monitoring and controlling avian influenza, The Guardian reported.

“Whether this novel H5N9 virus will cause human infections from its avian host and become a pandemic subtype is not known yet. It is therefore imperative to assess the risk of emergence of this novel reassortant virus with potential transmissibility to public health,” the US National Library of Medicine states on its website.

Avian influenza has had a profound impact globally, leading to extensive culling of poultry and affecting various mammalian species. In the United States, the spread of bird flu has contributed to rising egg prices and disruptions in the poultry industry. The detection of the H5N9 strain adds complexity to ongoing efforts to manage and mitigate the effects of avian influenza.

The Centers for Disease Control and Prevention (CDC) is closely monitoring the situation. While the risk to the general public remains low, the CDC emphasizes the importance of vigilance, especially among individuals who have direct contact with poultry. Proper biosecurity measures and prompt reporting of sick or dead birds are crucial steps in preventing the spread of the virus.

This incident underscores the need for ongoing surveillance and research to understand the dynamics of avian influenza viruses. The USDA and other relevant agencies are committed to working with industry stakeholders, health officials, and the public to address this emerging threat and safeguard both animal and human health.

As investigations continue, authorities will provide updates and guidance to ensure that appropriate measures are taken to control the outbreak and prevent potential transmission to other farms or species. The situation remains dynamic, and continued collaboration among federal, state, and local entities is essential in managing this evolving challenge.