Heard & McDonald Islands - Credit Wikipedia
#18,920
Today only Australia, NZ, and the islands of Oceania remain free of the HPAI H5 virus, and while they are protected by vast oceans, most experts expect the virus will arrive there eventually.
Australia does have indigenous LPAI viruses, which occasionally mutate into HPAI varieties. Last year we followed outbreaks of 3 different HPAI H7 viruses across 3 territories (see Australia: 11th Avian H7 Outbreak, Now Reported in ACT).
Oceania's protection has often been attributed to the Wallace and Weber lines; imaginary dividing lines used to mark the difference between animal species found in Australia and Papua New Guinea and the rest of Southeast Asia (see 2008 study Will Wallace’s Line Save Australia from Avian Influenza?).
These stark faunal differences also extend to birds, reptiles, and even insects.
Given movement data demonstrating connectivity between the polar front to both the Antarctic and Subantarctic islands of Oceania, and Oceania itself, it is plausible that if HPAI H5 were present in the Antarctic region directly south of Oceania, it could be introduced to Oceania.
Since 2022 we've also seen an Unprecedented `Order Shift' In Wild Bird H5N1 Positives, with many seabirds; including gannets, gulls, guillemots and great skua now hosting the virus.
This increased avian host range likely helped to facilitate the arrival of HPAI to Hawaii last year, and could potentially do the same for Oceania.
A little over a year ago we looked at an informative webinar, held by Australia's Biodiversity Council, on how they are preparing for HPAI H5's almost inevitable arrival. The 1-hour video is available on YouTube, and you'll find a link to a detailed summary below.
Note: Some of the video clips of affected birds may be hard for some people to watch.
While it is still far-removed from the Australian mainland, today the Australian government released a joint statement on the discovery of unusual mortality - consistent with HPAI H5 - among elephant seals on the remote island of Heard.
While HPAI H5 has not yet been confirmed (tests are pending), officials are obviously concerned enough to make this public announcement.
The full press release follows, after which I'll have a brief postscript.
Suspected H5 bird flu in elephant seals at Australian sub-Antarctic Island
Media release
Environment
Environment protection
24 October 2025
Joint DAFF & DCCEEW media statement
Australian scientists have observed signs consistent with H5 avian influenza (bird flu) in wildlife during a management voyage to sub-Antarctic Heard Island.
At this stage it is not a confirmed detection. It reinforces the need for Australia to remain focused on preparing for an outbreak.
Heard Island is part of the Heard Island and McDonald Islands external Australian territory. It’s over 4000 km south west of Perth and 1700 km north of Antarctica in the Southern Ocean.
Australia remains the only continent free from the highly contagious strain of H5 bird flu. A confirmed detection on Heard Island would not substantially increase the risk to Australia.
Scientists observed unusual levels of mortality in elephant seals on Heard Island in recent days.
Observations were made by Australian Antarctic Program scientists on an environmental management visit to the island on board the RSV Nuyina. There were no observations of unusual levels of mortality in other species present on the island, including penguins and other seabirds.
Seeing signs consistent with H5 bird flu in wildlife on Heard Island is not unexpected. This virus has previously been found on the French Kerguelen and Crozet sub-Antarctic islands, which are less than 450 km from Heard and McDonald Islands.
Samples have been safely collected and securely packaged in accordance with International Air Transport Association (IATA) Dangerous Goods Regulations.
The samples will be submitted to the CSIRO Australian Centre for Disease Preparedness for confirmatory testing when RSV Nuyina returns to Australia in mid November.
It will take some weeks to get the results from these tests.
The Australian Government is investing more than $100 million into strengthening bird flu preparedness and enhancing our response capacity. Further information is available at birdflu.gov.au
While the introduction of HPAI H5 has been impactful for every new country or territory it has conquered, when H5N1 arrived in North American birds we saw an immediate explosion in reassortments with local (North American) LPAI viruses, and the generation of scores of new genotypes.
As a result, the United States has seen new variants emerge capable of infecting cattle and other livestock, a marked increase in its ability to infect smaller mammals, including cats, mice, and the spillover into > 70 humans.
In addition to posing a devastating threat to Australia's ecology, Oceania's isolated, and HPAI-naive collection of LPAI viruses could conceivably provide the same sort of `accelerant' to H5N1's evolution.
While it is always possible that Oceania's LPAI viruses will prove less compatible with HPAI H5, this is an uncontrolled field experiment we really don't want to see take place.
Stay tuned.
