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 herds since last year.

The new version, known as D1.1, was confirmed in Nevada cattle and was linked to the first US death tied to bird flu ...