Researchers find concerning mutation in H5N1 bird flu found in Canadian teen

The Canadian teenager infected with the H5N1 bird flu virus in November 2024, has fully recovered, but researchers have raised concerns over the ‘worrisome’ mutations found in the virus isolated from her. In the case published Tuesday in the special edition of the New England Journal of Medicine, the researchers expressed their concern over the ominous mutation, which has potentially allowed the virus to target human cells more effectively, causing severe disease.
“Highly pathogenic avian influenza A(H5N1) virus infection acquired in North America can cause severe human illness. Evidence for changes to HA that may increase binding to human airway receptors is worrisome,” the authors said in the study. The case explored the H5N1 bird flu cases from 2024 in North America. In one study, the doctors and the research team observed a Canadian teenager, while in the other study, the public health officials from across the U.S. including the Centers for Disease Control and Prevention (CDC), and state and local health departments examined the 46 human cases that occurred between March and October 2024. 66 human cases of H5N1 bird flu were reported in the U.S. in 2024.
The 13-year-old Canadian girl, who had asthma and Class 2 obesity, was initially admitted to a local emergency room on Nov. 4 after experiencing conjunctivitis and fever. She had conjunctivitis for two days and fever for one day, before arriving at the emergency room. The girl was discharged the same day without any treatment. However, her condition deteriorated over the next three days, and she developed a cough, diarrhea, and vomiting. On Nov. 7, she was readmitted to the hospital due to respiratory distress and hemodynamic instability, a condition where the body struggles to maintain consistent blood flow and pressure.
By Nov. 8, the teenager was transferred to a pediatric intensive care unit at another hospital with respiratory failure, pneumonia, acute kidney injury, low platelet counts, and low white blood cell counts. She was tested negative for human seasonal influenza viruses, however, had high viral loads of influenza. This prompted the caregivers to run a bird flu diagnosis, and it came back positive. She was intubated and put on extracorporeal membrane oxygenation (ECMO), a life-support technique for severe heart or lung conditions, as the disease progressed over the next few days. The doctors administered three antiviral medications including oseltamivir, amantadine, and baloxavir.

Fearing a potentially fatal cytokine storm, which is an excessive inflammatory response, the doctors administered daily plasma exchange therapy. Her condition gradually improved, and by Nov. 16, she tested negative for the virus.
The authors point out that the viral load remained consistently higher in her lower lungs than in her upper respiratory tract, which suggests potential gaps in current diagnostic testing methods. She recovered completely and on Nov. 28, the girl was discharged.

Genetic sequencing of the virus isolated from the teenager showed the D1.1 strain of H5N1, a variant found in wild birds. Researchers noted that the mutations in the virus likely enhanced its ability to replicate in human cells, making it more pathogenic. Incidentally, similar mutations were also identified in a Louisiana patient, who developed severe illness. The mutation of the virus has raised concerns amongst scientists and healthcare experts. Experts caution that the virus’s ability to adapt in humans poses a significant threat.