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Why it's important to monitor bird flu on Svalbard
Svalbard lies far north in the Arctic. There is ice, extreme cold, and vast distances in this area. But this has not prevented avian influenza from spreading. Quite the opposite.
It started with a dead glaucous gull. In the summer of 2022, researchers detected highly pathogenic avian influenza (HPAI) in a glaucous gull near Longyearbyen.
Highly pathogenic means that a virus causes severe disease and results in extremely high mortality (close to 100 per cent) among infected birds.
This was the first documented case of the disease on Svalbard.
That same year, at least 27 dead great skuas were recorded in a single day on Hermansenøya. The following year, in 2023, researchers reported increased mortality among seabirds at several locations across Svalbard, particularly among black-legged kittiwakes.
But dead birds tell only part of the story.
Since then, the Norwegian Veterinary Institute has been working closely with a range of partners to track how the avian influenza virus moves between species and through Svalbard’s ecosystems.
Svalbard is not as isolated as it looks
Many people think of Svalbard as one of the most remote places on Earth.
But every summer, millions of migratory birds arrive here from Europe, Africa, North America, and the North Atlantic.
These birds connect the Arctic to the rest of the world and can carry viruses as unintended passengers on their journeys.
Between 2022 and 2025, researchers identified four different variants of avian influenza virus on Svalbard and Jan Mayen.
The findings suggest that migratory birds introduced avian influenza to the archipelago on multiple occasions, not through a single event.
“One particularly striking finding was that two different subtypes of highly pathogenic avian influenza virus, H5N1 and H5N5, were circulating simultaneously within a breeding colony of great skuas on Hermansenøya,” says Silje Granstad.
She is a researcher and poultry specialist at the Norwegian Veterinary Institute.
“When multiple virus variants meet within the same bird populations, they can exchange genetic material. This is something we want to monitor closely because such processes may lead to the emergence of new virus variants,” she says.
The virus spreads to mammals
In 2025, highly pathogenic avian influenza (H5N5) was detected in five Arctic foxes. They had either been found dead or were euthanised due to illness.
This marked the first time the Norwegian Veterinary Institute had detected avian influenza in mammals on Svalbard.
The findings showed that the virus was not confined to birds but had spread to other species within the Arctic ecosystem.
Even so, sick and dead animals provide only a limited picture of the situation. How widespread was the infection really?
To answer this question, researchers investigated whether the animals had previously been exposed to the virus. The method involves antibody testing.
When animals are exposed to sufficient amounts of a virus, their immune system produces antibodies. These remain in the body long after the infection has passed and can reveal previous exposure.
By measuring these antibodies, researchers can investigate how many animals have been exposed to avian influenza. The results surprised them.
Antibodies revealed hidden transmission
Researchers therefore tested both polar bears and Arctic foxes for antibodies. The analyses showed that none of the polar bears sampled before 2022 had antibodies against H5 avian influenza.
Yet by 2023, three out of four tested bears had antibodies.
In 2024 and 2025, more than 95 per cent of sampled polar bears carried evidence of previous infection.
The same pattern was observed in Arctic foxes. Researchers detected no antibodies in samples collected between 2006 and 2015.
However, during the winter of 2023–2024, 95 per cent of sampled Arctic foxes tested positive for antibodies against the virus.
“Antibody testing provides a completely different picture from simply detecting the virus in sick and dead animals,” says Johanna Hol Fosse.
She is a researcher at the Norwegian Veterinary Institute.
“The antibodies were detected in animals that were assumed to be healthy. This shows that the virus is far more widespread than we initially thought. At the same time, the findings suggest that many polar bears and Arctic foxes survive infection,” she explains.
When the virus reached the top of the food chain
In spring 2026, researchers made another remarkable discovery.
An adult walrus was found dead in the Raudfjord on Svalbard.
Shortly afterwards, guides observed a female polar bear and her one-year-old cub feeding on the carcass. Just over a week later, the cub was found dead.
The Norwegian Veterinary Institute helped collect samples from both animals and analysed them.
The results showed that the walrus and the polar bear cub were infected with H5N5 avian influenza viruses that were genetically almost identical.
Large quantities of the virus were detected in the brains of both animals. This strengthened the suspicion that avian influenza caused their deaths.
This was the first time avian influenza has been detected in a polar bear in Europe.
Avian influenza has previously been detected in polar bears in Alaska. A recently published study shows that polar bears in Greenland have also been exposed to the virus.
A warning from the north: Viruses adapting to mammals
Researchers have also identified findings that warrant particular attention.
Several virus samples detected in mammals on Svalbard carried genetic markers previously associated with the virus adapting to mammals.
Monitoring these changes matters because they can provide valuable insight into how influenza viruses evolve. This knowledge is essential for assessing risks and contributing to international preparedness against new influenza strains.
Although avian influenza viruses have infected several mammal species, there is still little evidence to suggest that they can spread efficiently to or between humans.
The Norwegian Institute of Public Health assesses the risk to the general public as very low. It is also considered low even for individuals who have come into contact with infected animals.
Monitoring in the Arctic is becoming increasingly important
One of the most important outcomes of these studies is that they reveal gaps in our knowledge. This demonstrates the need for long-term surveillance.
Because Svalbard serves as a natural meeting point for migratory birds from several continents, the archipelago is an important location for detecting changes in the virus at an early stage.
“No one would have known how widespread avian influenza was among Arctic foxes and polar bears on Svalbard if we had only examined sick and dead animals,” says Ingebjørg H. Nymo.
She is a senior researcher at the Norwegian Veterinary Institute.
The antibody studies showed that a large proportion of the animals examined had been exposed to the virus. Without regular sampling of live animals, this spread would have gone unnoticed, the researcher explains.
"We are therefore extremely grateful for our close collaboration with the Norwegian Polar Institute and for the extensive sample collections they have built up over many years through other research activities,” she says.
Viruses know no borders
“Avian influenza knows no borders. To understand how the virus moves between species and geographical regions, we need long-term, systematic surveillance programmes," says researcher Ragnhild Tønnessen.
She is the avian influenza coordinator at the Norwegian Veterinary Institute.
This involves both examining sick and dead animals and conducting studies that can reveal previous exposure in living animals, she explains.
“These different methods complement one another and provide a more complete picture of how the virus circulates in Arctic ecosystems. Top predators may serve as valuable indicator species for infection in regions where direct surveillance of bird populations is challenging,” she says.
Sources:
Fosse et al. Serological Evidence of Widespread Exposure to H5 Avian Influenza Virus in Arctic Foxes in Svalbard, Norway, BioRxiv, 2026. DOI: 10.64898/2026.09.17.752278
Granstad et al. Multiple introductions of highly pathogenic avian influenza viruses into the High Arctic: Svalbard and Jan Mayen, 2022–2025, Journal of General Virology, 2026. DOI: 10.1099/jgv.0.002305
Madslien et al. Highly Pathogenic Avian Influenza H5N5 in a Polar Bear and Atlantic Walrus, Svalbard, 2026, with Widespread Seroconversion in Polar Bears, BioRxiv, 2026. DOI: 10.64898/2026.07.20.739480
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