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.

The decision marks a rebuke of an idea floated by Trump administration officials in recent weeks to change the policy. More than 35 million birds have been killed in response to bird flu outbreaks in commercial flocks so far this year, according to the USDA's figures.

With egg prices soaring due to a severe bird flu outbreak, the U.S. Department of Agriculture (USDA) announced a $1 billion plan to contain the disease and help poultry farmers recover. The outbreak has destroyed flocks nationwide,