A person in the state of Louisiana has died from avian influenza or bird flu, also known as H5N1, the Louisiana Department of Health (LDH) reported on Jan. 6, marking the first recorded human fatality from H5N1 in the U.S.
“The patient contracted H5N1 after exposure to a combination of a non-commercial backyard flock and wild birds,” LDH said in its press release.
The department added its investigation had found no evidence the virus transmits from person to person. The patient, who was older than 65 years and reportedly had underlying medical conditions, “remains the only human case of H5N1 in Louisiana,” LDH said.
“Though H5N1 cases in the U.S. have been uniformly mild, the virus does have the capacity to cause severe disease and death in certain cases,” Dr. Amesh Adalja, infectious disease physician at the Johns Hopkins Center for Health Security, told Reuters.
Avian influenza viruses naturally occur in wild aquatic birds. Some of these viruses can also infect domestic poultry and other bird and animal species, with some strains causing minor symptoms, while others can be deadly.
A highly pathogenic avian influenza (HPAI) strain of the virus that emerged in Europe in 2020 has been particularly contagious and deadly. Mongabay previously reported that this strain has impacted at least 485 bird species and 48 mammal species, killing seals, sea otters, dolphins, foxes, albatrosses, bald eagles, pumas and polar bears. The current H5N1 animal pandemic has been aided by humans, Mongabay reported, with industrial-scale poultry farms helping the virus spread faster and more widely.
In the U.S., there have been 65 confirmed human cases of H5N1 bird flu since 2024, the Centers for Disease Control and Prevention (CDC) said. Most infected people are farmworkers exposed to known sick or infected farm animals, and have experienced minor symptoms.
In December, the CDC had analyzed samples of the H5N1 virus infecting the Louisiana patient and found the strain in the patient was more closely related to the one circulating in wild birds and poultry and different from the one spreading among dairy cattle in the country. The latter has been associated with more, but milder, human cases.
The CDC’s analysis also found that the virus infecting the patient seemed to have picked up mutations within the person. Those changes “were not found in virus sequences from poultry samples collected on the patient’s property, suggesting the changes emerged in the patient after infection,” the CDC said.
Seema Lakdawala, a microbiologist and immunologist at the Emory University School of Medicine, told CNN that while the evolution of the virus is concerning, it “highlights how we need to prevent each possible spillover infection to reduce the risk of onward transmission to others.”
The CDC said it’s continuing to monitor changes in H5 viruses and “that the risk to the general public remains low”.
Banner image: Colorized transmission electron micrograph of H5N1 virus particles (yellow). Image via Flickr by CDC and NIAID (CC BY 2.0)
This story first appeared on Mongabay
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