EXPERT REACTION: Avian flu's spread to remote Antarctic islands

The detection of highly pathogenic avian influenza virus (HPAI) in the Antarctic and sub-Antarctic regions is an alarming development, underscoring the vulnerability of these remote ecosystems to infectious diseases. The recent study detailed the presence of the H5N1 virus in various bird and mammal species on the sub-Antarctic islands of South Georgia and the Falkland Islands, and provides critical insight into how migratory birds may act as vectors for the virus to enter new regions. In this case, the virus most likely spread to South Georgia and the Falklands from South America, where infections have killed tens of thousands of seabirds and marine mammals. This raises significant concerns about the potential spread of the virus to other areas of Antarctica, especially during the upcoming Antarctic seabird breeding season.
 
Globally, tens of millions of birds have died of HPAI, with seabird populations being hit particularly hard. While this particular study did not detect the virus in mainland Antarctica, other researchers detected HPAI in February 2024 on the Antarctic Peninsula. This heightens fears that the virus could spread to more isolated regions via migrating birds and mammals. Populations of penguins and seals, already facing threats from climate change, may be at risk, however, so far penguins have not experienced the high mortality of other seabird species. 
 
Given the fragile nature of Antarctic ecosystems, it is crucial that we remain vigilant in monitoring the spread of HPAI. Enhanced surveillance efforts, coupled with international cooperation and real-time data sharing, will be vital in assessing the ongoing risk and mitigating the potential impact on wildlife.

"HPAI H5N1 clade 2.3.4.4b is responsible for a panzootic, or a global animal pandemic. This virus has been responsible for the death and/or destruction of millions of wild and domestic animals. In South America, more than 400,000 wild birds have been affected. It is extremely distressing to know that HPAI has entered the Antarctic region (including sub-Antarctic Islands and the Antarctic Peninsula). This virus has had substantial impacts on wildlife species, particularly in South Georgia Island, which has had knock on effects on the tourism industry.
 
This article is extremely timely, given that research teams (and tourists) will soon be returning to the Antarctic region for the austral summer season. The data here within provide critical insights into virus introduction and spread, which will be integrated into continued and future preparation and response activities in Antarctica.
 
The initial sequences from both the Falklands and South Georgia were made freely available months ago, demonstrating a commitment to open science and rapid data sharing. This study builds upon the initial pre-print with additional sequences and high resolution analysis, providing high resolution detail into sequence analysis, provide detailed case data, and proposes virus spread and movement within the region.
 
Given the concern around potential mammal-to-mammal transmission in marine mammals in South America, it is encouraging that the full genome sequences from elephant seals and a fur seal did not contain any PB2 mutations of interest. However, that some sequence from birds did include PB2 D701N, which has been reported in the marine mammal associated clade in South America, is of interest.
 
The last reported case in the Antarctic region was in March 2024, which co-indices with the end of the tourist and research season. Confirmed and suspected cases of HPAI in the Antarctic and sub-Antarctic can be accessed on our dashboard https://scar.org/library-data/avian-flu
 
Australia (Oceania) remains the only part of the planet free from Clade 2344b HPAI H5N1. The mostly likely route of virus introduction to Australia remains from the Asia, most likely with long distance migratory birds. At present, cases in Antarctica are limited to the Antarctic Peninsula, many thousands of kilometres from Australia. Thus, HPAI outbreaks in Antarctica likely pose a low risk to Australia, but if/when outbreaks occur in the region of Antarctica that is directly south of Australia, the risk of introduction via this route will change. An abridged version of a risk assessment for Australia can be found here, and consideration of the Antarctic route into Australia is discussed here."

"The recently published article, 'Detection and spread of high pathogenicity avian influenza virus H5N1 in the Antarctic Region' documents the first detection of H5N1 high pathogenicity avian influenza virus (HPAIV) in the Antarctic and sub-Antarctic regions, specifically South Georgia and the Falkland Islands. The research, conducted in late 2023, involved extensive field sampling and diagnostic testing across multiple avian and mammalian species.

Initial detection occurred in brown skuas on Bird Island, South Georgia, in October 2023, followed by confirmations in various other species including kelp gulls, black-browed albatross, and seal species. The study employed local RT-PCR testing and confirmatory analysis at international reference laboratories, along with genetic analyses to trace the virus's origins. Results indicated that the virus likely spread from South America via migratory birds.

The introduction of HPAIV poses a significant threat to the unique and vulnerable ecosystems of the Antarctic region, which had previously been untouched by such pathogens. The study's findings underscore the need for enhanced biosecurity measures and continued surveillance to monitor and mitigate the spread of the virus, particularly given the potential impact on already vulnerable seabird populations.

While the genetic composition of the H5N1 virus detected in Antarctica shows similarities to strains found in South America, the study did not find any unique adaptive mutations in the Antarctic strains that would increase the risk to human populations compared to other global instances of H5N1 infections. This finding is crucial because H5N1 is known for its potential to cause severe disease in humans, and mutations that increase transmissibility or virulence could pose significant public health risks. Monitoring the genetic composition of the virus is essential to detect any changes that might enhance its threat to humans or wildlife.

This is an important paper documenting that highly pathogenic avian influenza (HPAI) has spread into Antarctica and the subantarctic Islands for the first time. It is of great interest and concern to us as it provides us with some information on how the virus is behaving in previously unexposed seabirds and mammals, which allows us a better risk assessment of the virus making its way into Oceania, the last continental area of the world unaffected by this clade of the virus. There is cause for some hope in that penguin species haven’t been severely affected to date, and that while marine mammals in the subantarctic have been severely affected there is no evidence yet of transmission between mammals.

However, the species of seabirds now known to be affected is of concern for us in New Zealand, as many of these species -- such as skua, giant petrels, kelp gulls and albatross species -- have circumpolar ranges which include the subantarctic island in New Zealand territory and the mainland of New Zealand. With the movement of HPAI into Antarctica, the risk of the virus making its way to New Zealand is increasing.

New Zealand is home to incredible seabird diversity with 96 breeding seabird taxa and the highest global diversity of albatross, petrels, penguins and shags. Many of these species are critically endangered, with several in significant decline. The impact of HPAI on these populations could be severe, and could spill over into the island retreats we use for the conservation management of many other endangered species of birds, such as kākāpō, and rowi. If HPAI makes it to mainland New Zealand, then it could become a threatening process for our most critically endangered species like southern dotterels, shore plovers and fairy prions.

The Ministry of Primary Industries and the Department of Conservation have been working to prepare for any incursion of HPAI into New Zealand, but this paper demonstrates that its difficult to predict which species of birds and mammals may be affected and how badly their populations will be affected.
 

This study details the detection of clade 2.3.4.4b H5N1 highly pathogenic avian influenza virus (bird flu) in the Antarctic and sub-Antarctic regions off the coast of South America.

The authors confirmed H5N1 in many species, including both the southern fulmar and black-browed albatross. These species, along with many others, migrate northward from Antarctica to New Zealand, South America and Australia, highlighting the very real threat that this virus could be introduced to New Zealand via such migratory birds.

By generating virus genomes, this study showed that the sequences from South Georgia and the Falkland Islands clustered with H5N1 viral sequences obtained from South America between October 2022 and October 2023.

While, for now at least, HPAI seems to have had relatively low impact to Antarctica, it is vital to continue to understand the frequency of viral introductions and spread into this region by generating and sharing virus genomes. Nevertheless, there are a limited number of sequences deposited in public databases from H5N1 detections in South America, which hugely limits interpretation. This study illustrates the usefulness of virus genomes and highlights the need for rapidly generating and openly sharing them.

This study provides evidence on the viral transmission pathway via migratory birds, which is both interesting and important. However, since some wild animal populations in the Antarctic region are indeed at risk of HPAI, the conclusions of low impact to penguin species seems under-supported, particularly since it is not accompanied by the explicit caveat that this comes from a very limited sample. More evidence is likely needed for such conclusions, such as from investigations incorporating robust sampling efforts and targeted carcass searches.