A patient has been hospitalized in Louisiana with a severe case of avian influenza A(H5N1) virus (“H5N1 bird flu”) infection. This is the first instance of severe illness linked to the virus in the United States.
The Centers for Disease Control and Prevention confirmed the case on December 13 and announced it today on their website. Since April 2024, there have been 61 reported human cases of H5 bird flu reported in the United States.
Partial viral genome data of the H5N1 avian influenza virus that infected the patient in Louisiana indicates that the virus belongs to the D1.1 genotype related to other D1.1 viruses recently detected in wild birds and poultry in the United States and recent human cases in British Columbia, Canada, and Washington state. This H5N1 bird flu genotype is different than the B3.13 genotype detected in dairy cows, sporadic human cases in multiple states, and some poultry outbreaks in the United States.
Additional genomic sequencing and efforts to isolate the virus from clinical specimens from the patient in Louisiana are underway at the CDC.
While an investigation into the source of the infection in Louisiana is ongoing, it has been determined that the patient had exposure to sick and dead birds in backyard flocks. This is the first case of H5N1 bird flu in the U.S. that has been linked to exposure to a backyard flock.
According to the CDC, a sporadic case of severe H5N1 bird flu illness in a person is not unexpected; avian influenza A(H5N1) virus infection has previously been associated with severe human illness in other countries during 2024 and prior years, including illness resulting in death. No person-to-person spread of H5 bird flu has been detected. This case does not change the CDC’s overall assessment of the immediate risk to the public’s health from H5N1 bird flu, which remains low.
The CDC also warns that in addition to affected commercial poultry and dairy operations, wild birds and backyard flocks can also be a source of exposure. People with work or recreational exposure to infected animals are at higher risk of infection. They should follow recommended precautions when around animals that are infected or potentially infected with the H5N1 avian influenza virus. Backyard flock owners, hunters, and other bird enthusiasts should also take precautions.
The best way to prevent H5 bird flu is to avoid exposure whenever possible. Infected birds shed avian influenza A viruses in their saliva, mucous, and feces. Other infected animals may shed avian influenza A viruses in respiratory secretions and other bodily fluids (e.g., in unpasteurized cow milk or ‘raw milk’).
As a general precaution, people should avoid contact with sick or dead animals, particularly wild birds and poultry whenever possible.
