A version of the H5N1 virus that has killed one person and severely sickened another has been detected in milk samples collected from Nevada dairy herds.

Experts said the discovery raises questions about how widely the virus has spread, and underscores the difficulty of controlling infections among animals and people working with them. View on euronews

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.