Limited Outbreak of Highly Pathogenic Influenza A(H5N1) in Herring Gull Colony, Canada, 2022

Abstract

In summer 2022, highly pathogenic influenza A(H5N1) virus reached the herring gull (Larus argentatus subspecies smithsonianus) breeding colony on Kent Island, New Brunswick, Canada. Real-time monitoring revealed a self-limiting outbreak with low mortality. Proactive seabird surveillance is crucial for monitoring such limited outbreaks, protecting seabirds, and tracing zoonotic transmission routes.

Keywords: American herring gulls; H5N1; HPAI; Larus argentatus subsp. smithsonianus; avian flu; avian influenza virus; bird flu; gull; highly pathogenic influenza A(H5N1) virus; influenza; influenza in birds; interclass transmission; poultry diseases; respiratory infections; seabird; viruses; zoonoses.

Figure 1

Location of gull breeding colony on Kent Island, New Brunswick, Canada, in study of limited outbreak of highly pathogenic influenza A(H5N1) in herring gull colony, 2022. A) Inset shows location of Kent Island in Canada. The main study site was on East Beach (yellow strip), and a secondary site was on West Beach (purple strip). Intermittent monitoring occurred across Kent, Hay, and Sheep Islands. Satellite image from Google Earth (https://earth.google.com). B) Accumulating carcass locations (red points) for 3 timepoints on East Beach.

Figure 2

Adult herring gull deaths (cumulative, end-of-day) on East Beach, Kent Island, New Brunswick, Canada, in study of limited outbreak of highly pathogenic influenza A(H5N1) in herring gull colony, 2022. A) Cumulative mortality of herring gulls on East Beach during summer 2022. B) Census counts (number of breeding and nonbreeding adult herring gulls) from 1–3 surveys/day on East Beach and weekly total counts from surveys of the entire island. Red dotted lines mark July 6, the date of maximum gull deaths on East Beach.