This makes it the third confirmed case of bird flu in a polar bear worldwide, but evidence suggests exposure on Svalbard is far more widespread.
A second polar bear on Svalbard has tested positive for highly pathogenic avian influenza (HPAI), commonly known as bird flu, only a few months after the first case was confirmed in a polar bear on the archipelago.
The young bear was found dead on Æøya, near Virgohamna in northern Spitsbergen, in June. Samples collected by the Governor of Svalbard were later analysed by the Norwegian Veterinary Institute, which announced on August 25 that H5N5 avian influenza had been detected in both nasal and brain samples. The animal was also tested for rabies, with negative results.
This is only the second confirmed detection of bird flu in a polar bear in Norway and Europe.
Two cases only 23 kilometres apart
The first European case was confirmed in May, when a young male polar bear found dead in Raudfjorden tested positive for H5N5. A dead walrus found in the same area was also infected.
The two infected bears were found around 23 kilometres apart. The earlier discovery in Raudfjorden prompted researchers to recommend testing the bear that had already been found on Æøya.
With the latest finding, bird flu has now been scientifically reported in polar bears on only three occasions worldwide. The first known case involved a young male found dead in Alaska in August 2023.
Exposure appears much more widespread
The rarity of confirmed cases does not, however, mean that encounters between polar bears and avian influenza are equally rare.
Research carried out by the Norwegian Veterinary Institute together with the Norwegian Polar Institute and other partners has found evidence of previous avian influenza exposure in a large proportion of the Svalbard polar bears examined since 2022. The findings suggest that the virus is circulating among the bears and that exposure extends well beyond the animals in which infection has been detected after death.
Both infected Svalbard bears were young animals. Researchers say this adds to indications that younger polar bears could be particularly susceptible, as has also been observed in some other carnivorous mammals. However, the Veterinary Institute stresses that evidence remains limited. Scientists still know little about what avian influenza infection means for individual polar bears or for the population as a whole.
Further analysis of the virus from the latest case is planned, including investigation of whether it shows signs of adaptation to mammalian hosts.
Bird flu at both poles
Polar Journal has also been closely following developments related to bird flu in Antarctic and sub-Antarctic wildlife. There, recent outbreaks have involved H5N1, a different subtype from the H5N5 detected in the two Svalbard bears.
Highly pathogenic avian influenza had never been detected in the Antarctic region before late 2023. Today, it is present in wildlife at both poles, with recent evidence of infections across a growing range of species. At the same time, much remains unknown about its implications for polar wildlife and ecosystems, making continued monitoring and research increasingly important.
Dr. Yana Kirichenko