Rare H5N9 Bird Flu Detected in U.S. for the First Time on California Duck Farm

For the first time, the United States has reported an outbreak of the rare H5N9 strain of bird flu in poultry, according to the World Organisation for Animal Health (WOAH). The outbreak was confirmed on a duck farm in Merced County, California, where the more common H5N1 strain was also detected.

The U.S. Department of Agriculture (USDA) confirmed that nearly 119,000 birds on the affected farm were culled by December 2 to prevent further spread. In its report to WOAH, the USDA stated, “This is the first confirmed case of HPAI H5N9 in poultry in the United States.”

Highly pathogenic avian influenza (HPAI), often referred to as bird flu, has become a global concern in recent years. The H5N1 strain has been responsible for most of the devastation, resulting in the culling of hundreds of millions of birds worldwide. It has also been detected in dozens of mammal species, including dairy cows in the U.S., and has caused at least one human fatality in Louisiana.

The H5N9 strain, while less common, is being closely monitored due to its potential impact on both animal and public health. The USDA Animal and Plant Health Inspection Service (APHIS), in collaboration with state health and wildlife officials, is conducting extensive investigations and increased surveillance in response to these outbreaks.

California’s Merced County is now a focus of enhanced biosecurity measures to curb the spread of these bird flu strains. While bird flu primarily affects poultry, experts are keeping a close watch as the virus continues to adapt and spread among different species.