Cows infected by lethal bird flu strain showing respiratory symptoms, Nevada says

At least four cattle herds in Nevada have tested positive for a strain of H5N1 bird flu never before seen in cows, state agriculture officials confirmed Wednesday, and respiratory symptoms like coughing and sneezing have been reported.

That bird flu strain, called D1.1 by scientists, was also linked to a fatal human case in Louisiana last year after exposure to sick birds. The D1.1 strain has emerged in recent months to dominate infections in wild birds and poultry flocks across North America.

Symptoms seen in humans infected by D1.1 have been more severe than the previous bird flu strain that has been spreading in cows. That strain, called B3.13, has led to only mild symptoms, like pink eye and fever, in humans infected after contact with sick cows.