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Although most of the world is primarily concerned with HPAI H5N1, in northern Europe, Iceland, and parts of Canada, a different avian flu subtype - HPAI H5N5 - has been making inroads as well.
In the summer of 2022, the Norwegian Veterinary Institute reported both H5N1 and H5N5 for the first time in wild birds on Svalbard, which lies above the Arctic circle (see More HPAI (H5N5 & H5N1) Detected In Arctic (Svalbard).Additionally, here in the United States HPAI H5N5 infected and killed a resident of Washington State last November, following contact with backyard birds.
Although no other animals were confirmed infected during this investigation, there were eye witness accounts of two other polar bears exhibiting potential neurological symptoms.
Five weeks ago, in Preprint: HPAI H5N5 in a Polar Bear and Atlantic Walrus, Svalbard, 2026, with Widespread Seroconversion in Polar Bears, we saw a report indicating that H5N5 exposure is far more common among polar bears on Svalbard island than previously thought.
Somewhat surprisingly, most polar bears appear to survive H5N5 infection, although severe (and likely neurotropic) illness can occur.
Yesterday the Norwegian Veterinary Institute reported on a second polar bear - recovered in June some 23 km distant from the one found in May - has tested positive for H5N5.
(translation)
Bird flu detected in another polar bear in Svalbard
Published 25.08.2026
The Norwegian Veterinary Institute has detected avian influenza in a young polar bear found dead on the northern tip of Spitsbergen. This is the second time the virus has been detected in polar bears in Norway and Europe.
The detected highly pathogenic avian influenza (HPAI) virus is of the subtype H5N5, a type of the virus that has been previously detected in Svalbard: In wild birds for the first time in 2022 , in a walrus in 2023 , in arctic foxes in 2025 , and in a polar bear and walrus in the spring of 2026. This latest detection is the second in polar bears in Norway and Europe.
Highly pathogenic avian influenza viruses have also previously been detected in carnivorous mammals such as red foxes, otters and lynxes on mainland Norway after infection from wild birds.
Sampled in the field by the District Governor
The polar bear, a young individual, was found dead on Æøya, near Virgohamna. The animal was sampled by the Governor in June 2026, after avian influenza virus was detected in a dead polar bear and a dead walrus in Raudfjorden in May 2026. The distance between the two findings of dead animals is approximately 23 kilometers.
- After the findings on the polar bear and walrus in Raudfjorden, we also recommended sampling the polar bear that was on Æøya, says veterinarian and wildlife health specialist at the Veterinary Institute Knut Madslien.
The samples from the polar bear were then sent to the Norwegian Veterinary Institute and tested for avian influenza virus and rabies. Highly pathogenic avian influenza virus was detected in samples from both the brain and nose. Rabies virus was not detected.
Bird flu virus is circulating in the highlands
"The findings are part of a trend where highly pathogenic avian influenza virus is increasingly being detected in mammals in Europe. At the same time, the virus has spread to new areas in recent years, including the Arctic, where it may have consequences for vulnerable populations and ecosystems," explains Ragnhild Tønnessen, avian influenza coordinator at the Norwegian Veterinary Institute.
- Our researchers, in close collaboration with the Norwegian Polar Institute and other partners, have found that a large proportion of the polar bears examined in Svalbard after 2022 have been exposed to previous avian influenza infection. Although we currently have limited knowledge of the consequences this has for the polar bears, the results indicate that the virus is circulating in the population and that exposure is more widespread than detections in dead animals alone would indicate, says Tønnessen.
Increased infection pressure in mammals
Most avian influenza viruses are best adapted to be transmitted between birds. However, mammals can sometimes be infected through direct contact with sick or dead birds or other mammals infected with the virus.
The Veterinary Institute will conduct further investigations of the detected virus to characterize it more closely and clarify whether it shows signs of being specifically adapted to mammals.
Second detection in polar bears in Europe
In other predators, such as red foxes and lynxes, avian influenza can cause clinical signs of brain disease. Neurological signs such as circling gait, tilted head position, paralysis and reduced shyness towards humans are common.
Avian influenza virus in polar bears has been scientifically published twice previously: In a young male polar bear found dead in Alaska in August 2023 and in a young male polar bear found dead in Raudfjorden on Svalbard in May 2026. However, it is not known how the virus affects individual individuals or the population of polar bears.
– This finding strengthens the indications that highly pathogenic avian influenza virus can also affect polar bears, and that young individuals are particularly vulnerable. This is also consistent with findings in other carnivorous mammals, where the virus mainly affects younger individuals. However, the knowledge base is still very limited and it is important to gain more knowledge about how the virus can affect polar bears, says Madslien.
Report if you observe dead or sick animals and birds
Both highly pathogenic avian influenza and rabies are serious diseases found in Svalbard and can be transmitted to humans. Contact with sick and dead animals should therefore be avoided.
If sick or dead animals are observed on Svalbard, it is important that the findings are reported to the Governor . This is important to obtain an overview of disease incidence and mortality, although it does not always trigger sampling. If avian influenza is suspected in birds and other animals on the mainland, the Norwegian Food Safety Authority must be notified .
The Norwegian Veterinary Institute is the national reference laboratory for avian influenza and has molecular methods for the detection and characterization of avian influenza viruses.
Admittedly, HPAI H5N5 remains a minor player in the world of avian flu, but it has shown remarkable tenacity, persisting and even thriving in some high latitude regions of the Northern Hemisphere.
A recent study (see J. Virology: Risk assessment of avian influenza A(H5N5) virus from the first human case using the ferret model) found that while the Washington State isolate replicated robustly in mammalian cells and caused severe disease, it still lacked adaptations supporting efficient airborne spread.
Six years ago HPAI H5N8 subtype dominated the world's avian flyways, only to be abruptly supplanted by a new and improved H5N1 in 2021.
A reminder of just how quickly the avian flu-scape can change, and why we continue to watch this subtype with interest.
