Climate change is helping the H5N1 bird flu virus spread and evolve

The spread of the highly pathogenic avian influenza virus H5N1 among animals is unprecedented having been found on all continents—except Oceania—with the United Nations calling it "a global zoonotic animal pandemic."

H5N1 is known to be able to infect over 350 species of birds and close to 60 species of mammals with migratory waterfowl—including ducks, swans, geese and gulls—being especially susceptible to various avian-borne influenza viruses.

H5N1-infected waterfowl are normally asymptomatic carriers, however, these birds can infect other species (including mammals) along their migratory routes. This global transference allows disease to spread, and for virus genetics and virulence to continually adapt.

Alarmingly, evidence indicates that climate change seems to be impacting the emergence of zoonotic viruses like H5N1. As global climate conditions change, avian migratory patterns and routes are also changing.

Higher temperatures and extreme weather has resulted in large-scale population shifts in a range of temperate species. These changes have led to diseases emerging in areas—and in genetic configurations—entirely unique and unprecedented.

H5N1 is a clear indication that disease monitoring and response efforts are an essential part of any climate change adaptation and mitigation strategy.

H5N1

The ecology and genetics of H5N1 viruses have evolved significantly since first being detected in China in 1997.

The H5N1 virus has been detected in the polar regions and the first confirmed case of a polar bear dying from H5N1 was recorded in Alaska in 2022. Antarctica has seen significant rates of mortality in its native elephant and fur seal populations as a result of viral exposure.

Non-migratory wild birds are highly susceptible to H5N1 infections brought on the wings of their more transitory cousins. There have been approximately 75,000 bird casualties globally as per the World Animal Health Information System. However, efforts to accurately estimate the total number of wild birds which have died as a result of H5N1 are hampered by issues in data quality and availability.