Updated December 18, 2024 at 17:54 PM ET
California Gov. Gavin Newsom has declared a state of emergency in response to the ongoing spread of bird flu among dairy cattle.
The declaration is a sign of growing concern over the situation in California, which has become the epicenter of the nation's outbreak in cattle.
More than 300 dairy herds have tested positive in California in the last 30 days alone.
The governor said that cases detected in dairy cows on farms in Southern California showed that expanded monitoring and a more coordinated statewide response is needed in response to the outbreak.
"This proclamation is a targeted action to ensure government agencies have the resources and flexibility they need," Newsom said in the statement.
"While the risk to the public remains low, we will continue to take all necessary steps to prevent the spread of this virus."
California currently accounts for about half of known human infections in the U.S.
There's no evidence of ongoing human to human spread in California or the rest of the country. But scientists warn that uncontrolled spread in dairy cattle heightens the risk of spillover into humans, which could give the virus a chance to acquire dangerous mutations.
The move also comes on the heels of another troubling development – the country's first case of severe illness detected in a human.
On Wednesday, officials with the Centers for Disease Control and Prevention shared additional findings about that infection in a resident of Louisiana who was hospitalized after being exposed to sick and dead birds in backyard flocks.
Genetic sequencing indicates the H5N1 virus responsible for the illness belongs to a genetic lineage that's circulating in wild birds and poultry — different from what's spreading in dairy cattle and driving the majority of infections in agricultural workers.
In the U.S., more than 60 people have been infected so far, although some research suggests the official tally may be an undercount.
The illnesses linked to dairy cattle have largely led to mild illnesses in humans.
The version of the virus in the Louisiana case is the D1.1 genotype. It has previously popped up in poultry workers in Washington state, who developed mild symptoms after testing positive in October. More recently, however, a teenager in British Columbia was hospitalized after contracting this D1.1 strain of the virus.
Canadian health officials were unable to figure out how that person was infected.
The case in southwest Louisiana was detected during routine flu surveillance and eventually sent to the CDC for confirmation. The case doesn't change the CDC's assessment that the risk to the general public remains low.
Still, the hospitalization is a reminder that bird flu has a well-established history of leading to severe illness and death over the past 20 years in other countries, Dr. Demetre Daskalakis with the CDC, told reporters on Wednesday during a press call.
Daskalakis said his agency is doing additional sequencing to look for any worrying changes in the virus that could signal it's evolving to better infect humans or cause more severe disease.
Scientists were concerned that the case in British Columbia exhibited certain mutations that could spell trouble, although more research was needed to understand the exact implications.
Daskalakis referred reporters to Louisiana officials conducting the investigation into the case for further details on how the person caught the virus and their symptoms.
As with the Louisiana infection, most cases have been linked back to some kind of exposure to sick animals. Dairy cattle harbor high loads of virus in their milk and that's suspected to be causing infections in farm workers. Those working with infected poultry can also catch the virus.
However, several cases have cropped up in the U.S. that can't be tracked back to infected farm animals, including in California and Missouri.
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