Only 10 viral particles cause H5N1 avian flu infection in cows

Just 10 viral particles of the H5N1 bird flu that caused hundreds of influenza outbreaks in U.S. dairy cattle can cause infection in cows, a new study shows. The research also hints at why the outbreaks have confounded scientists, farmers and livestock handlers hoping to contain and prevent the disease—an effort likely complicated by the fact that the virus has an affinity for cow mammary glands rather than airways.