Cows have human flu receptors, research shows, raising stakes on bird flu outbreak among dairy cattle

At the beginning of March, Dr. Barb Petersen, a large animal veterinarian in Texas, gets calls from the dairy farms she works with in the Panhandle. Workers there saw many cows with mastitis, an udder infection.

Their milk was thickened and discolored, and this couldn't be explained by the usual suspects like bacteria or tissue damage.

A number of other dairies called. One owner told her he thought his farm "had everything going on, and half of my pets had died," indicating the infestation had spread beyond just livestock.

After running a series of tests and ruling out every cause ...