The strain of bird flu is distinct from what has previously been found in dairy cattle. The finding means the virus has again spilled over from birds to cows, and it raises some worrying questions.

Dairy cattle in Nevada have been infected with a new type of bird flu that’s different from the version that has spread in U.S. herds since last year, Agriculture Department officials said Wednesday.

The U.S. Department of Agriculture has detected a bird flu strain in dairy cattle that previously had not been seen in cows, according to an email from the agency's Animal and Plant Health Inspection Service seen by Reuters.