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A newly identified antiviral-resistant strain of highly pathogenic avian influenza (H5N1) has been detected in Canadian poultry farms, according to a research letter published in Emerging Microbes and Infections. Scientists have identified a rare neuraminidase (NA) protein mutation, known as H275Y, which exhibits resistance to oseltamivir, a commonly used antiviral treatment for influenza.
Mutation Raises Treatment Challenges
Researchers at the National Centre for Foreign Animal Disease in Winnipeg, Canada, analyzed viral isolates from eight poultry farms and confirmed the presence of the H275Y mutation. While North American strains of H5N1 have historically descended from Eurasian lineages, the recent outbreak in British Columbia in October 2024 exhibited a distinct NA segment of North American origin.
The study revealed that the identified mutation could undermine the effectiveness of oseltamivir, one of the primary antiviral drugs used for both treatment and prevention of influenza. “The continued circulation of viruses harboring NA-H275Y may necessitate a re-evaluation of influenza treatment strategies in Canada,” the researchers warned.
Potential Human Health Risks
Although resistance to oseltamivir remains uncommon, past outbreaks of avian influenza—such as those in Vietnam in 2005—have shown similar resistance patterns. Dr. Jose A. Lucar, an infectious disease expert at George Washington University, explained that influenza viruses are highly mutable and capable of genetic reassortment, a process that can lead to drug-resistant variants.
“In this report, researchers identified a reassortant H5N1 virus with a mutated neuraminidase gene segment from a low-pathogenic avian influenza virus, conferring oseltamivir resistance in Canadian poultry,” Dr. Lucar noted. “While the public health risk remains low, clinicians should be vigilant for potential human cases, particularly in individuals with exposure to infected birds or raw dairy products.”
Public health officials emphasize the importance of clinical history in suspected cases of avian flu. Individuals who have been in contact with sick or deceased birds, livestock, or unpasteurized dairy products within ten days of illness onset should seek medical evaluation.
Treatment and Research Gaps
If antiviral resistance is suspected in a human patient, clinicians are advised to send respiratory samples for laboratory testing. In cases of confirmed oseltamivir resistance, zanamivir is the preferred alternative treatment.
Dr. Lucar highlighted a critical research gap: “Previous studies suggested that H275Y mutations reduce viral fitness, but this outbreak suggests otherwise, as the virus has rapidly spread across multiple farms. Further research is needed to assess the implications of this mutation and refine therapeutic strategies should oseltamivir resistance become more widespread.”
Health officials continue to monitor the situation, urging poultry workers and healthcare professionals to remain cautious and follow infection control measures.
Disclaimer:
This article is for informational purposes only and does not constitute medical advice. Individuals concerned about avian influenza exposure should consult a healthcare professional or public health authority for guidance.
