US Investigates Worrying Bird Flu Strain on Duck Farm in California

  • International group reports first US case of H5N9 in poultry
  • Virus has been linked to ‘severe human respiratory infections’

The H5N9 version is thought to come from a genetic combination of other bird flu viruses, including H5N1.

Photographer: Philippe Lopez/AFP/Getty Images
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US officials are investigating the appearance of a strain of bird flu identified in the US for the first time, a worrying sign that the virus is evolving in ways that could make it harder to contain.

Detected on a duck farm in Merced County, California, it’s the first confirmed case of H5N9 in poultry in the US, according to the website for the World Organization for Animal Health, a Paris-based group focused on animal diseases.