Riccardo Liguori The H5N1 virus has caused the death of millions of birds and mammals around the world, putting biodiversity at risk. Despite its alarming spread, its impact is still little reported
@Canva
The deadly trail from the H5N1 avian flu virus is ever-widening, now reaching as far as Antarctica according to the results of a new study published in Nature Communications.
Having swept the globe since 2021, the resultant bird death toll has surpassed 280 million birds, making it the greatest sudden decline of the world’s wild bird population in decades. But birds are by no means the only ones to have taken hits; tens of thousands of mammals have been infected by the virus, with outbreaks even taking place in Antarctica, where elephant seals and fur seals are dying in droves.
Despite its global reach, the impact this epidemic is-or could be-having on biodiversity, agriculture, and human health has been curiously under-discussed. “I don’t believe the public is really aware of how important avian influenza is,” said Prof Ashley Banyard, a virologist with UK’s Animal and Plant Health Agency, in an interview with the Guardian.
A global epidemic
Originating in 1996 on a poultry farm in China, the H5N1 virus became the dominant world strain of avian influenza in 2021. Since that time, the virus has spread to every continent except Oceania, where it causes mass die-offs of wild birds and sometimes even decimates complete populations.
Ornithologist Peter Stronach was among the first people to have seen it all over and over. In May 2022, he discovered dozens of dead birds lying on Littleferry Beach in Scotland-something that had never happened during this time of year. The scenario had only continued to get worse over the coming months as thousands of dead seabirds were reported.
The flu has brought about the most drastic and sudden loss of bird life seen in decades. Some of the longest-living seabird species may take years to recover. Such an outbreak has most drastically affected species with narrow geographic ranges.
It is reckoned that one-third of the world’s population of Svalbard barnacle geese are dead in the Solway Firth. Across Europe, 40% of the population of Dalmatian pelicans-a species found only in Southeastern Europe-was wiped out. Three-quarters of Britain’s great skuas at monitored sites have disappeared. Over 20 000 South American sea lions have died from HPAI in Peru and Chile-about 9% of the regional population.
A constantly evolving threat
Avian influenza is a contagious, fast-spreading disease. Since the virus exists in feces, mucus, blood, and saliva, this makes it highly contagious-a single sick bird may infect up to 100 birds. A teaspoon of infected feces can kill a whole house of chickens or turkeys; mortality rates can go as high as 100%.
Mammals have not escaped the epidemic either. In early March 2024, for the first time, an avian flu virus began spreading among U.S. cattle. Presently, over a hundred herds are known to have been affected; naturally, very many cases have probably gone unreported.
The Risk to Humans
As the virus continues to evolve, that threat may rise. As of this date, nine human cases of H5N1 have been documented in the United States, but overall the symptoms had been mild. To this date, there is no indication that H5N1 is being transmitted between humans, but in those instances when humans have contracted the virus by coming into contact with an animal that is infected with the virus, mortality rates are over 50%.
The future of the epidemic
In October 2023, the virus reached the Antarctic region and killed hundreds of seals in South Georgia. The scientists fear the actual death toll may be much higher because it is so challenging to monitor wildlife across such a huge area.
Although some species, like penguins, appear less affected, the situation is still alarming. The virus is constantly evolving and therefore may become more virulent or contagious. Experts emphasize further monitoring and increasing public awareness about the impact of avian flu on the environment.
