Bird flu thought to have killed Californian cows

Disease has infected 120 herds in California, the top milk-producing state, and was recently spreading in California at a rate of 15 farms per week

Bird flu has been found in more than 300 dairy herds in 14 states. Picture: Crystal Heath via Reuters

There are signs of bird flu being much more severe in dairy cows in California, perhaps linked to very hot weather in the state's Central Valley, which has the highest dairy farming density in the USA.

Since last March, bird flu has been found in more than 300 dairy herds in 14 states, and since the end of August, it has infected 120 herds in California, the top milk-producing state. It was recently spreading in California at a rate of 15 farms per week.