First Severe H5N1 Bird Flu Case in Louisiana Linked to Backyard Flocks
A patient has been hospitalized in Louisiana with a severe case of avian influenza A(H5N1), marking the first instance of severe illness linked to the virus in the United States. The Centers for Disease Control and Prevention (CDC) confirmed the diagnosis on Friday, December 13, 2024. This case is the 61st human infection of H5 bird flu reported in the U.S. since April 2024.
Origin and Viral Characteristics
Preliminary viral genome sequencing by the CDC indicates the patient was infected with the D1.1 genotype of the H5N1 virus. This specific genotype has been identified in wild birds and poultry across the U.S., as well as in recent human cases in British Columbia, Canada, and Washington state. The D1.1 genotype differs from the B3.13 genotype, which has been associated with dairy cow outbreaks and other sporadic human cases in the U.S.
Investigation into the patient’s exposure history reveals contact with sick and dead birds within a backyard flock. While the CDC continues its genomic sequencing and virus isolation efforts, this incident represents the first U.S. case of H5N1 linked specifically to a backyard poultry setting.
The Louisiana case is the first instance of severe H5N1 illness in a person linked to a backyard flock in the United States, though sporadic severe cases have been documented in other countries in 2024 and prior years.
Public Health Risk Assessment
The CDC maintains that the immediate risk to the public’s health from H5N1 remains low. There has been no detected person-to-person spread of the virus. Health officials note that sporadic cases of severe illness are not unexpected, given the virus’s history of causing serious health complications globally.
The identification of the D1.1 genotype in this patient underscores that the risk of exposure is not limited to commercial dairy or poultry operations. As the virus continues to circulate in wild bird populations, individuals interacting with backyard flocks or wildlife may face higher risks, highlighting the necessity of adhering to established safety protocols.
Preventative Measures and Next Steps
Avoiding exposure is the most effective way to prevent infection. The virus is shed through the saliva, mucous, and feces of infected birds, and through respiratory secretions or bodily fluids of other animals, including unpasteurized “raw” milk. The CDC advises the public to avoid contact with sick or dead animals, particularly wild birds and poultry.
For those with necessary close contact with animals, the use of personal protective equipment (PPE) is recommended. Future updates on the situation may be tracked through the official H5 Bird Flu: Current Situation page. Analysts expect that continued genomic monitoring will be essential to track how different genotypes, such as D1.1 and B3.13, evolve in the domestic animal population.
Frequently Asked Questions
How did the patient in Louisiana contract the virus?
The CDC investigation determined the patient had direct exposure to sick and dead birds in a backyard flock.
Is this the same virus affecting dairy cows?
No. Genomic data shows the patient was infected with the D1.1 genotype, which is distinct from the B3.13 genotype identified in dairy cows and other sporadic U.S. cases.
Has the public health risk level changed?
No. The CDC reports that the immediate risk to the public remains low, as there is no evidence of person-to-person transmission.
What precautions do you take when interacting with wildlife or domestic animals on your property?