Health officials say the 65-year-old was hospitalised after contact with an infected flock of back-yard birds.
A 65-year-old in the southern state of Louisiana has been hospitalised in critical condition as the result of the bird flu, becoming the first severe case reported in the United States.
The Centers for Disease Control and Prevention (CDC) announced on Wednesday that the person had been in contact with an infected flock of back-yard birds. There have been no reported cases of person-to-person transmission.
“CDC confirms first severe case of H5N1 Bird Flu in the US. While an investigation into the source of the infection is ongoing, it has been determined that the patient had exposure to sick and dead birds in backyard flocks,” the agency said.
“This case does not change CDC’s overall assessment of the immediate risk to the public’s health from H5N1 bird flu, which remains low.”
Demetre Daskalakis, director of CDC’s National Center for Immunization and Respiratory Diseases, also told reporters that the Louisiana case was the first to be linked to a noncommercial flock.
While experts emphasise the threat to public safety is minor at present, the spread of the virus has raised questions over how the outbreak is being tested and tracked.
As of Wednesday, the CDC has tallied 61 confirmed human cases of bird flu in the US, with most of them connected to exposure to sick poultry or dairy cows.
Avian flu, or H1N1, is endemic — or regularly occurring — among wild bird populations. But its presence among livestock and domesticated animals has raised the likelihood of human infections.
The CDC said a strain of bird flu was first detected among US dairy cattle on March 25. “This is the first time that these bird flu viruses had been found in cows,” it said.
Shortly thereafter, on April 1, Texas reported the first human transmission from exposure to a dairy cow. Since then, 37 of the 61 human bird-flu infections have been linked to herds of infected dairy cattle, with California tallying 33 of the cases.
According to the US Department of Agriculture (USDA), there are 865 infected herds across 16 states. On Wednesday, California declared a state of emergency to try to stem the outbreak.
“This proclamation is a targeted action to ensure government agencies have the resources and flexibility they need to respond quickly to this outbreak,” Governor Gavin Newsom said in a statement.
His statement emphasised that California boasts “the largest testing and monitoring system in the nation to respond to the outbreak”.
“While the risk to the public remains low, we will continue to take all necessary steps to prevent the spread of this virus,” Newsom said.
Some farmers have opposed the push to test commercial livestock for bird flu, and the US government itself has largely resisted imposing mandatory testing, relying on voluntary efforts instead.
That stance, however, shifted on December 6, when the US Department of Agriculture’s Animal and Plant Health Inspection Service announced it would be testing samples of raw, unpasteurised milk from herds nationwide.
The federal order requires any dairy farm, milk transporter or dairy processing facility to share raw milk samples upon request.
Herd owners are also mandated to share any information related to the spread of disease among their cattle in order to allow federal authorities to trace the spread of bird flu.
But the B3.13 genotype associated with bird flu in cattle is distinct from the strain in the Louisiana case, known as the D1.1 genotype. The CDC confirmed that case on Friday but did not announce its findings until Wednesday.
In two cases — one of a child in California and another of an adult in Missouri — the CDC has not yet determined how the patients were infected. A Canadian teen was also hospitalised last month with a severe case of bird flu.
Bird flu has killed 123 million poultry since the outbreak first began in the US in 2022.