A polar bear died from bird flu for the first time. What is the highly pathogenic avian influenza?

For the very first time, a polar bear has passed away because of bird flu. The incident took place in Alaska
The death of the polar bear was confirmed in December by the Division of Environmental Health officials. The dead polar bear was found in October in Utqiagvik. The reason for death in this bizarre incident is the highly pathogenic avian influenza (HPAI). Influenza can be caught in cases of scavenging on bird carcasses that have been infected with the H5N1.
On one side, the Arctic population is struggling to bear with climate change, and if the bird flu spreads, it will add to the woes.
Is it the first time for bears to contract with such a virus? 

Well, previously, brown and black bears have been acquainted with the virus. The incident of polar bear passing away due to the virus, however, seems to be more alarming as the species is already a vulnerable one. The species is troubled with a myriad of severe problems such as losing their sea habitat, making it difficult for them to survive. 
Now, the concern is that if in vase influenza spreads among the species, it can drastically bring down its already low population. 

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The highly pathogenic avian influenza (HPAI) 

It was in the year 1996 when the H5N1, a strain of the highly pathogenic avian influenza (HPAI) was identified for the very first time in China. However, the virus has now spread all across the world. A new variant of the virus came in the year 2020. The deadly virus variant killed a great number of birds. It spread across North America as well later.
In those years while humans were struggling with the pandemic caused by the coronavirus, the H5N1 and its variants killed thousands of mammals. 

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Are polar bears at risk due to the virus?

Polar bears live in a habitat where detecting the virus among the species can turn out to be an extremely difficult task. This puts polar bears at risk. 

However, what serves as a ray of hope is the fact that since polar bears are solitary species, the risk of transmission of the virus stands low. Yet, the situation is still alarming, as the species is facing reduced sea ice, due to which it has begun to feed on seabirds more. 

Another concerning factor in the case of polar bears is their very low population, which thereby makes the species more vulnerable. The species get adversely affected by anthropogenic chemicals. These accumulate in the high-fat diets of animals. Now, since the fat store gets depleted, the stored pollutants begin affecting the immune system. 
A polar bear who hasn't eaten anything for a long time is definitely deprived of nutrition, resulting in a weak immune system. When polar bears come in contact with such viruses, it becomes very difficult for their immune systems to fight influenza.

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