First U.S. detection of virulent H5N9 strain, at a California duck farm, draws scrutiny as evidence of genetic reassortment that could trigger human outbreaks.

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

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,