the United States he has now seen dozens of cases of human bird flu this year, all mild—so far.
The Centers for Disease Control and Prevention confirmed Wednesday that a patient in Louisiana was hospitalized with a severe case of bird flu caused by the H5N1 virus. This marks the first case of serious illness linked to the virus in the US.
The virus has decimated flocks of chickens and wild birds across the country and infected more than 800 dairy herds in 16 states. Infected animals have been spreading the virus to people they come into contact with. Since April, the US has seen a total of 61 cases of bird flu in eight states. Of those, 37 were exposed to sick or infected dairy cows, and 21 were exposed to chicken farms and social media. In those cases, people develop conjunctivitis and mild respiratory symptoms and make a full recovery.
The severe case is important because bird flu has previously been associated with severe illness in other countries, including outbreaks that resulted in 50 percent mortality. From 2003 to 2023, out of 878 people tested for the virus, 458 died.
An investigation by the Louisiana Department of Health and the CDC has determined that the hospitalized patient, a resident of southwest Louisiana, was exposed to sick and dead birds in backyard flocks. This is the first case of H5N1 bird flu in the US linked to exposure in a domestic flock, rather than a commercial farm.
“While the investigation into the source of the virus in Louisiana is ongoing, it is believed that the patient reported by Louisiana was exposed to sick or dead birds in his area,” said Demetre Daskalakis, director of the CDC’s National Center for Immunization. and Respiratory Diseases, during a press conference on Wednesday. No other information was available on the source of exposure or the condition of the patient.
A person with bird flu in Missouri was hospitalized in late August, but CDC officials said it was due to underlying medical conditions. The patient had no respiratory symptoms and was not seriously ill from his infection. “In the case of Missouri, we don’t really have the same kind of data to support that it was related to their flu,” Daskalakis said.
There is genetic similarity between the Louisiana patient’s virus and the virus from a Canadian teenager who was hospitalized with H5N1. Scientists have isolated the virus in Louisiana as type D1.1, the same strain found in the Canadian patient and another case from Washington state. This variant has also been found in wild birds and poultry in the US.
This is different from the B3.13 strain, which has been found in dairy cattle, in other poultry diseases, and in rare human cases in many states. CDC scientists performed additional genomic sequencing of the Louisiana patient’s virus sample. Genomic sequencing can identify possible changes in the virus that may indicate increased ability to infect humans or be transmitted from person to person.
So far, no human-to-human transmission of H5N1 bird flu has been detected. The CDC says the risk to public health remains low, but those with occupational or recreational exposure to infected animals are at high risk of contracting the virus. “This means that backyard flock owners, hunters, and other bird enthusiasts should take precautions,” the organization said in a statement.
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