H5 bird flu spreads between birds inside Australia

By Caleb Reed · 2026-07-29

The moment Australia's border defence broke down

H5 bird flu was first detected in a greater crested tern found at Robe, South AustraliaverifiedVerified Source: pir.sa.gov.au, a finding that triggered intensive surveillance across coastal colonies.^[1] Genetic analysis confirmed what authorities had been dreading: the virus was no longer simply arriving on migratory birds from overseas. It was moving between birds already inside the country.

Federal Agriculture Minister Julie Collins said the confirmation of local transmission changed the nature of the response. "While there remains no evidence of any mass mortalities at this point in time, we do expect, with this local transmission, that there will be further detections in Australian wildlife," Collins said.^[7]

What H5 bird flu is and how it travels

H5 bird flu, formally H5N1 clade 2.3.4.4b, is a highly contagious strain of avian influenza that causes severe outbreaks in poultry and high death rates in wild birds and some mammals overseas.^[6] Migratory waterfowl and shorebirds carry it long distances, shedding the virus in droppings, respiratory secretions and contaminated water.

Avian influenza viruses can mutate from low pathogenicity to high pathogenicity forms after entering poultry flocksverifiedVerified Source: agriculture.gov.au, which is why detection in wild birds close to farmland is treated as a serious early warning.^[6] Griffith University infectious diseases ecologist Hamish McCallum said the spread to a local seabird was very bad news.^[8]

Why a tern colony is a threat to a chicken shed

Greater crested terns nest in dense coastal clusters and share habitat with migratory species carrying the virus. An active outbreak inside such a colony amplifies infection pressure, raising the chance that sick birds drift towards farmland and encounter domestic flocks.^[3]

Poultry farms that allow wild birds access to free-range sheds or water sources face the highest introduction risk. The federal agriculture department said the virus can spread through direct contact between birds or through environments contaminated by infected droppings or feed.^[6] Free-range egg and chicken meat operations along the South Australian and wider southern coastline sit closest to the affected seabird colonies.

The case count and how it spread across four states

Australia recorded 12 confirmed or presumed positive detections as of 10 July, a figure that climbed to 17 by 17 July.^[2][3] South Australia leads the national count with 14 confirmed cases as of 28 July, with Western Australia recording 10, New South Wales 2 and Queensland 1.^[4]

New South Wales confirmed its first case in a giant petrelverifiedVerified Source: nsw.gov.au, marking the virus's entry into that state's wildlife.^[5] Samples from the latest detections have been forwarded to CSIRO for final laboratory confirmation, the standard protocol for novel or escalating detections in Australia.

What farmers and authorities are doing next

The federal agriculture department confirmed there remains no evidence of any mass mortality events and no detections of H5 bird flu in poultry or agricultural production systems as of 17 July.^[3] The department said the risk to human health from H5 bird flu in Australia remains low, with authorities urging poultry producers to review on-farm biosecurity, restrict wild bird access to sheds and water sources, and report any unusual bird deaths immediately.

Collins's warning that further wildlife detections are expected signals a sustained surveillance effort is now under way. South Australia's primary industries department had recorded 14 confirmed cases in wild seabirds by 28 July 2026.^[4]

Caleb Reed

Caleb Reed covers breaking news and sport. He works to the rhythm of a story as it unfolds, and he is happiest when the facts arrive faster than anyone can spin them.