A particularly deadly variant of the bird flu virus H5N1 has been rampant worldwide since 2021, and millions of birds have already died. Now this influenza virus has also reached Antarctica: Biologists have now detected H5N1 in skuas on an Antarctic island for the first time. The virus was probably introduced by returning migratory birds. Scientists now fear that this bird flu, which is usually fatal to birds, could quickly spread to other Antarctic islands and West Antarctica.
The influenza virus not only causes annual flu waves in humans - numerous, often fatal flu viruses are also rampant among birds. Particularly in Asia, the mass farming of poultry repeatedly creates new bird flu variants, which are then spread via migratory birds to Europe and beyond. While the bird flu variants that are naturally rampant among wild birds are not very aggressive and an infection is therefore usually harmless, this is often different with the virus variants from poultry: they are usually highly pathogenic and kill up to 100 percent of the infected birds.
A deadly bird flu is spreading
One such deadly variant of the H5N1 flu virus strain developed in Asia in 2021 and has since spread almost worldwide. This virus mutant is a descendant of the H5N1 influenza, which was widespread a few years ago, but is slightly modified and is even more contagious and aggressive. By the beginning of 2022 alone, more than 15 million wild birds had died from this bird flu variant. Mammals, especially marine mammals such as seals and sea lions, have also become infected and died in large numbers. “The current wave of bird flu H5N1 is unprecedented in its rapid spread and the extremely high frequency of outbreaks in poultry and wild birds,” warned the World Health Organization (WHO) at the beginning of 2022.
Since autumn 2022, this highly pathogenic H5N1 bird flu has also been spreading in South America; it has now even been detected in birds at the tip of Tierra del Fuego. “More than 500,000 seabirds have died from H5N1 since arriving in South America, primarily pelicans, boobies, cormorants and penguins,” reported Meagan Dewar from the Antarctic Wildlife Health Network and her colleagues in the summer of 2023. Even then, this raised fears that what would happen next Antarctica could also be affected. Many Antarctic bird species stay on the Falkland Islands and in the southern part of South America during the polar winter. “Species such as the Dominican gull or the brown skuas move back and forth between South America and the Antarctic Peninsula and have therefore long been considered important vectors for the introduction of highly pathogenic bird flu into the Antarctic region,” explain Dewar and her team.
First evidence in Antarctic skuas
This is exactly what has apparently happened now: In October 2023, biologists from the British Antarctic Survey (BAS) detected the highly pathogenic variant of H5N1 for the first time in birds on the Antarctic island of Bird Island. Several brown skuas (Stercorarius antarcticus), a sub-Antarctic species of skuas, tested positive for H5N1. “These are the first known cases in the Antarctic region,” said the British Antarctic Survey. Bird Island is part of South Georgia, an archipelago located off the tip of the West Antarctic Peninsula in the South Atlantic. These islands are home to many colonies of sub-Antarctic and Antarctic seabirds and marine mammals. “The presence of the highly pathogenic influenza virus on these islands could have serious consequences for the local seabird colonies,” warns the BAS.
The discovery of the first H5N1 cases on Bird Island raises concerns that the bird flu virus could quickly spread to other Antarctic islands and West Antarctica. “Highly mobile seabird species and young birds that move between colonies will be the main spreaders of the virus,” said Dewar and her colleagues. In addition to seagulls, these also include Antarctic albatrosses and penguins. “In species like the black-browed albatross, ten to 30 percent of the subadult population move back and forth between colonies every day,” say the researchers.
It could therefore only be a matter of time before the deadly H5N1 virus spreads to other parts of Antarctica.
This poses an acute and deadly threat to birds and marine mammals in the southern continent. The H5N1 virus is also an acute threat to mammals in southern polar latitudes. By August 2023, almost 10,000 sea lions had died from H5N1 in Peru alone, and there were further deaths in fur seals, elephant seals and coastal otters. Biologists from the British Antarctic Survey and the Antarctic Wildlife Health Network will now continue to closely monitor the situation in South Georgia and West Antarctica. As a further precautionary measure, increased biosecurity measures are in place for all polar researchers in South Georgia.
Source: British Antarctic Survey, SCAR Risk Assessment Report