In a stark acknowledgment of the increasing seriousness of bird flu’s spread, Gov. Gavin Newsom of California declared on Wednesday that the outbreak of infections among the state’s dairy cattle constituted an emergency.
The announcement followed news earlier in the day that an individual in Louisiana had been hospitalized with bird flu, the first infected American to become severely ill.
The virus, H5N1, cannot yet spread easily among people, and it still poses little danger to the average American. Pasteurized dairy products are still safe to consume.
But the past few weeks have brought a steady drumbeat of cases in people, dairy cattle, birds and other animals. Each infection gives the virus a chance to take on a form that could cause a pandemic, experts warned.
“All these infections in so many species around us is paving a bigger and bigger runway for the virus to potentially evolve to infect humans better and transmit between humans,” said Dr. Nahid Bhadelia, the director of the Boston University Center on Emerging Infectious Diseases.
“That represents an escalation in the situation, even if risk to general population remains low,” she said.
California has borne the brunt of the outbreak in cattle.
The first herds in the nation infected with the bird flu virus, H5N1, were identified in March. California identified its first infected herd in late August.
But since then, the state’s agriculture department has found the virus in 645 dairies, about half of them in the past 30 days alone.
California has also recalled raw milk products from two companies after the virus was detected in samples.
Earlier this month, a child in Alameda County, in the Bay Area, tested positive for bird flu, but the source of infection was unclear. The child had no known exposure to infected animals.
A second child in the state was thought to have become infected from drinking raw milk, but the Centers for Disease Control and Prevention was unable to confirm the pathogen as H5N1.
The declaration of an emergency gives state and local health authorities additional means to contain the outbreak, including hiring staff and issuing new contracts.
“This proclamation is a targeted action to ensure government agencies have the resources and flexibility they need to respond quickly to this outbreak,” Mr. Newsom said in a statement. “While the risk to the public remains low, we will continue to take all necessary steps to prevent the spread of this virus.”
Federal and state governments may declare a public health emergency as a way to gain extra muscle to deal with a disaster. During the Covid-19 pandemic, the declaration of a nationwide emergency allowed the government to provide free tests, treatments and vaccines to Americans.
It also granted funds to public health departments, hospitals and nursing homes to help manage the pandemic.
Experts praised California’s action as a proactive step to contain the outbreak.
“California has been a leader in looking for the infections,” Dr. Bhadelia said. “The emergency powers will allow greater coordination and ability to apply more funds.”
The outbreak in dairy cattle is thought to have begun in Texas early this year. As of Wednesday, 865 infected herds had been identified in 16 states.
The C.D.C. has also confirmed H5N1 infection in 61 people, and has indicated another seven as “probable” cases. More than half of the confirmed cases have been in California.
Only 37 of the 61 cases have been traced to interaction with infected cattle; the remaining cases either have been attributed to exposure to diseased birds or other animals, or are of unknown origin.
The Louisiana resident who was hospitalized with H5N1 contracted the virus from a backyard flock, according to the C.D.C.
Seasonal flu vaccines do not protect against bird flu. The national stockpile holds a few million doses of H5N1 vaccine, and officials can order more should they be needed.
Several companies are also developing new vaccines for use in people or in cows.
H5N1 has been circulating in wild birds in the United States since early 2022, and it has since been identified in nearly every state. Cows are not typically susceptible to this type of influenza, but H5N1 appears to have acquired mutations in late 2023 that allowed it to jump from wild birds to cattle in the Texas Panhandle.
The virus then appears to have spread on dairy farms from Texas to Kansas, Michigan and New Mexico. In at least a dozen instances since, H5N1 has also spilled from cows back into wild birds, and into poultry, domestic cats and a raccoon.
Many experts, including those at the World Health Organization, have faulted the U.S. response to the outbreak.
Until recently, nearly all testing of cattle and of people who might have been infected with the virus had been voluntary. Only about one in 1,000 dairy farms was voluntarily testing its milk supply.
The Agriculture Department said earlier this month that it would begin testing the nation’s milk supply for H5N1, and that it would require farmers and dairy processors to provide samples of raw milk on request from the government.
California’s testing and monitoring system is the largest in the nation, as is the state’s dairy industry, which accounts for about 20 percent of the country’s milk supply.
