ARS TECHNICA – The outbreak of H5N1 bird flu in US dairy cows has now spread to three herds in California, the largest milk-producing state in the country, with around 1.7 million dairy cows, federal and state health officials have confirmed.
Fourteen states and 197 herds have now been affected by the unprecedented outbreak in dairy cows, which was first confirmed by federal health officials on March 25.
In a statement, the secretary of the California Department of Food and Agriculture, Karen Ross, said the spread of the virus to California was not unexpected.
“We have been preparing for this possibility since earlier this year when [Highly pathogenic avian influenza or HPAI] detections were confirmed at dairy farms in other states,” Ross said.
“Our extensive experience with HPAI in poultry has given us ample preparation and expertise to address this incident, with workers’ health and public health as our top priorities.”
“In 1996, highly pathogenic avian influenza H5N1 virus is first identified in domestic waterfowl in Southern China.” – CDC
Virus on the move
The herds in California are thought to have been infected through the movement of cattle, despite a federal order mandating testing of cattle prior to movement between states.
So far, health officials believe that all of the dairy infections across the affected states stem from a single spillover event from wild birds to dairy cows in Texas. The virus is thought to spread from cow to cow, as well as from contaminated milking equipment, hands, and boots.
Wild bird populations worldwide have been devastated by H5N1 in recent years, with its spread in the US first documented in 2022.
But, unlike past avian influenza outbreaks in wild bird populations, the current strain of H5N1 spreading—clade 2.3.4.4b—has proven unusually adept at spilling over to various mammals.
For instance, the US dairy outbreak marked the first time the virus was documented to cause an outbreak among cows …
