#19,306
Less than a year ago HPAI H5N1 was detected on Heard Island - an Australian external possession 4000 km south west of Perth - resulting in the the deaths of thousands of marine mammals and seabirds (see Preprint: Mass mortality of southern elephant seals during multi-species outbreak of HPAI H5N1 on sub-Antarctic Heard Island).
Drone surveys revealed mass mortality in southern elephant seals, with 8,573 pups (62%) recorded dead across Heard Island by the final surveys. Mortality increased at an average rate of 5.6% per day in a subset of harems, and the highest observed mortality in a harem was 97%. Based on the average (76%) mortality in the final surveys, total estimated pup mortality at Heard Island was 13,359 (from a total population of 17,364 pups), though this may be an underestimate as mortality was ongoing at this time.
Just over 2 months ago HPAI H5N1 arrived - via migratory birds - to the Australian mainland. Since then we've been watching as thousands of birds - both migratory and local - have succumbed to the virus.
23 August 2026
Attributable to Australian Chief Veterinary Officer, Dr Beth Cookson:
Testing at CSIRO’s Australian Centre for Disease Preparedness (ACDP) has confirmed H5 high pathogenicity avian influenza (bird flu) in a long-nosed fur seal, found at Beachport in South Australia. This is the first detection of H5 bird flu in a mammal species in Australia.
Although this is a concerning development, it is not unexpected that H5 bird flu has been detected in other wildlife, particularly marine mammals, in areas where there are high levels of infection in wild birds.
From 12 August 2026, we have changed how we report on H5 bird flu detections. Reporting will be based on events, rather than individual detections. See birdflu.gov.au for the latest information.
There remain no detections in poultry or in our agricultural production system.
The risk to human health remains low.
We get a few more details from the SA August 23rd update, which reads in part:
The long-nosed fur seal was found dead with no signs of injury and reported to the EAD hotline by a member of the public on Wednesday, 19 August. It was not reported as a suspect detection initially as state-based testing was inconclusive. However, samples were dispatched to ACDP for urgent testing which confirmed the H5 bird flu detection.
Based on the HPAI carnage we've seen among marine mammals elsewhere in the world (see UC Davis: High pathogenicity Avian Influenza in Pinniped conservation), today's announcement likely only heralds a much larger impact.
And while the Australian government still reminds the public that poultry and agricultural livestock remain unaffected, how long that happy status quo will stand is anyone's guess.
