Avian influenza in wild birds

Updated 19.05.2025

In 2020, highly pathogenic avian influenza (HPAI) was detected for the first time in wild birds in Norway. A number of detections of HPAI H5N1 in wild birds have been done so far this season (2021/2022).

Avian influenza (AI) is monitored in wild birds and in poultry.

The surveillance programme for AI in wild birds serves as a potential early detection and monitoring system in relation to influenza A viruses of avian origin, with special emphasis on HPAI H5 and H7 subtype viruses in the wild bird reservoir.

The main goal of the surveillance programme for AI in poultry is to document that Norwegian poultry flocks are free of influenza A infections of the subtypes H5 and H7.

Background

Avian influenza (AI) is cased by influenza A viruses, which are highly contagious, extremely variable viruses that are widespread in birds. Wild waterfowl such as ducks, geese, swans, waders and gulls are the natural reservoir for all low pathogenic influenza A virus subtypes. These virus carriers do not usually develop clinical disease, but shed large amounts of virus in their faeces.

In domestic poultry infection with influenza A viruses causes two main forms of disease, distinguished by high and low pathogenicity (ability to cause disease). Most of the low pathogenic AI (LPAI) viruses cause only mild disease in poultry, however LPAI strains of H5 or H7 subtype have the potential to mutate to highly pathogenic AI (HPAI) viruses following introduction to poultry populations. HPAI viruses induce a serious, highly contagious disease of poultry and other captive birds. The mortality in poultry flocks may in some cases be more than 90 %. All HPAI epidemics known so far have been of hemagglutinin subtype H5 or H7.

Even though avian influenza predominantly infects birds, some subtypes of avian influenza may occasionally infect humans after close contact with infected birds. In Asian countries, human infection with avian influenza subtypes H5N1 and H7N9 are associated with live poultry markets.

2023

Influenza A virus was detected in 164 of 926 wild birds examined in the surveillance programme for avian influenza in Norway in 2023. Active surveillance detected influenza A virus in 52 birds, of which one was characterised as highly pathogenic avian influenza (HPAI) H5Nx. Passive surveillance detected influenza A virus in 112 birds, of which 102 were identified as HPAI H5. Eighty-four of the HPAI detections in wild birds in 2023 were H5N1, eight were H5N5, and ten were H5Nx. Of sixteen wild mammals tested as part of passive surveillance, one red fox (Vulpes vulpes) tested positive for HPAI H5N1.

Download report

Avian influenza in wildlife 2023 (pdf 2mb)

Previous reports

Avian influenza in wild birds 2022 (pdf 2mb)
Avian influenza in wild birds 2021 (pdf 2mb)
Avian influenza in wild birds 2020 (pdf 758kb)
Avian influenza in wild birds 2019 (pdf 833kb)
Avian influenza in wild birds 2018 (pdf 2mb)
Avian influenza in wild birds 2017 (pdf 789kb)
Avian influenza in wild birds 2016 (pdf 2mb)
Avian influenza in wild birds 2010 (pdf 621kb)
Avian influenza in wild birds 2009 (pdf 465kb)
Avian influenza in wild birds 2007 (p. 115) (pdf 6mb)
Avian influenza in wild birds 2006 (p. 115) (pdf 3mb)
Avian influenza in wild birds 2005 (p. 109) (pdf 4mb)