Public health experts still don’t know how a bird flu virus has been spreading for months among dairy cows in the US – though early evidence points to contaminated milking equipment.
Since late March, 51 dairy herds across nine US states have tested positive for H5N1, a bird flu virus that has killed millions of birds and thousands of mammals worldwide. Genetic analysis of samples from infected cattle suggests the outbreak began when cows on a Texas farm contracted the virus from wild birds. It…