3e - Highly Pathogenic Avian Influenza A H5N1 infections in domestic poultry and human contacts in the Fraser Health region, British Columbia, Canada
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Background : Since 2022, Highly Pathogenic Avian Influenza (HPAI) A (H5N1) virus infections, coinciding with migratory bird seasons, have affected farmed poultry in British Columbia (BC), Canada. Majority of Infected Premises (IP) were in the Fraser Health (FH) region. We compared HPAI activity over two seasons in FH and assessed public health interventions uptake for human contacts to identify changes in distribution of HPAI detections and understand implications for practice.
Methods : We performed descriptive analysis on IP reported in the 2022-23 and 2023-24 seasons to assess geographic and temporal distribution of HPAI detections in farmed poultry. We calculated proportions of human contacts potentially exposed to HPAI A H5N1 for contacts management.
Results : During the 2022-23 and 2023-24 seasons, there were respectively 72 and 49 HPAI infected poultry premises, accounting for 89% and 96% of notifications in BC. Compared with the prior season, 2023-24 season peaked earlier, was shorter, had fewer IP reported per week and was more widespread across FH. There were 146 and 103 human contacts identified in 2022-23 and 2023-24 seasons respectively. Seasonal influenza vaccine and post-exposure prophylaxis acceptance were low. Of the 4 symptomatic contacts reported in both seasons, no human cases were detected. In the 2023-24 season, 45% of contacts identified with high exposure risk were lost to or refused follow-up.
Conclusions Our findings highlight the critical role of surveillance and characterization of human exposures to HPAI to swiftly identify cases, describe epizootics emergence, and inform risk assessment and interventions. Engaging with agricultural partners and swift information sharing from national to regional levels across public and animal health authorities are recommended for effective prevention and control strategies, more importantly given recent HPAI detections in livestock.