The Pennsylvania Department of Agriculture confirmed the positive case Monday in a 50,000-bird layer chicken flock on a commercial poultry farm in Lehigh County.

The United States has reported its first outbreak of H5N9 bird flu in poultry on a duck farm in California, the World Organisation for Animal Health (WOAH) said on Monday.

A person working on a farm has contracted the human version of avian flu. The UK Health Security Agency (UKHSA) said the individual "had close and prolonged contact with a large number of infected birds", but would not say where the farm was. The person was "currently well and was admitted to a High Consequence Infectious Disease unit," it said.

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.

Bird flu cases are still rising in the U.S. as the virus continues to devastate poultry farms. More than 145 million chickens, ducks, turkeys and other fowl have been slaughtered across the United States since the outbreak began in January 2022.

This story incorporates reporting fromU.S. News & World Report, cidrap.umn and scmp.com.The United States has reported its initial outbreak of the H5N9 bird flu strain in poultry, specifically at a duck farm in Merced County,

British health authorities said they had detected a case of bird flu (H5N1) in a person in central England. The person acquired the infection on a farm, where they had close and prolonged contact with numerous infected birds,