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Norwegian Surveillance Found HPAI H5N5 and H5Nx in Common Gulls and Other Influenza A in Lesser Black-backed Gulls

Adult common gull in breeding plumage flying over Oppdal, Norway
Research · Disease, parasites & microbiology

Norway’s 2025 avian-influenza surveillance found different virus patterns in two common gull species. Four common gulls (Larus canus) were confirmed with highly pathogenic avian influenza (HPAI): three with H5N5 and one with H5Nx. H5Nx means that highly pathogenic H5 was confirmed but the neuraminidase (N) subtype was not determined. In active surveillance, influenza A virus was also detected in three of 25 common gulls and five of 20 lesser black-backed gulls (Larus fuscus), but none of those active-surveillance gull samples was recorded as H5-positive.

The distinction reflects two different surveillance routes. Active surveillance used planned sampling of live or hunted wild birds, while passive surveillance focused on birds found dead or moribund. The four HPAI detections in common gulls are therefore separate from the three influenza A-positive common gulls listed in the active-surveillance table.

The sample fractions should not be read as national infection rates. Three positives among 25 common gulls and five among 20 lesser black-backed gulls describe only the birds included in active surveillance; the programme was designed to detect and characterise circulating viruses, not to estimate prevalence in the national populations.

Across all 880 wild birds examined in Norway in 2025, 161 tested positive for influenza A virus and 77 were confirmed with HPAI H5. The national report, released through the Norwegian Veterinary Institute’s surveillance page on 19 August 2026, recorded HPAI in 18 wild bird species. For common gulls and lesser black-backed gulls, the results document virus detections in the sampled birds but do not by themselves show effects on survival, breeding success or population trends.

Sources and image credit

  1. Ytrehus, B., Granstad, S., Gjerset, B., Tønnessen, R., & Åkerstedt, J. (2026). The surveillance programme for avian influenza (AI) in Norwegian wildlife 2025. Report 35/2026.Primary national surveillance report. In 2025, four common gulls were confirmed with HPAI: three H5N5 and one H5Nx. Active surveillance separately detected influenza A in 3 of 25 common gulls and 5 of 20 lesser black-backed gulls; neither species had H5-positive samples in the active-surveillance table.
  2. Avian influenza in wild birdsOfficial surveillance page providing publication context and the national 2025 summary.

Image: Adult common gull (Larus canus) in breeding plumage flying above Oppdal, Norway, 23 June 2023. Photo: Charles J. Sharp / Wikimedia Commons. CC BY-SA 4.0. Representative lead image; the story also covers lesser black-backed gulls and does not depict a sampled bird. · CC BY-SA 4.0 · Source

About this content: This story was produced with AI assistance within an editorial workflow developed by Wildlife Vagabond. Editorial responsibility remains with Wildlife Vagabond.How AI is used

Disease, parasites & microbiology

SPECIES IN THIS STORY

Species in this story

Common Gull Larus canus Explore species Lesser Black-backed Gull Larus fuscus Explore species

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