Recently a suspected case of deadly [H5 bird flu], also known as high pathogenicity avian influenza (HPAI) H5N1, was confirmed in a brown skua in Australia. This large seabird was found in Cape Le Grand National Park near Esperance, about 700 km south-east of Perth in Western Australia. The virus is also suspected to have affected another seabird, a southern giant petrel, found at the same area. Following the initial testing, samples collected from these birds were sent to the CSIRO to confirm the first Australian cases of H5N1, specifically the clade 2.3.4.4b H5N1 lineage. Avian influenza viruses are categorised by subtype (creating the H and N number combination, here H5N1) and specific clades within the H5 subtype. This virus has devastated wildlife populations in other continents, and this could be the start of a long push to protect Australian birds and wildlife in Australia. Where did this virus come from? Avian influenza viruses, of which HPAI H5N1 is just one kind, have been around for millenia. In the vast majority of cases they cause no disease in birds. These strains are referred to as low pathogenicity avian influenza viruses. However, in 1996 one of these viruses evolved to become disease causing, and since then, this HPAI H5N1 has caused severe disease in poultry, and has become endemic in poultry. With chickens now forming about 70 per cent of all birds worldwide, this is a critical reservoir where the virus continues to evolve. The devastating effect of HPAI H5N1 is unfortunately not limited to poultry. Since 2021, HPAI H5N1 has caused a global animal pandemic, with enormous consequences for wildlife in all continents. It has killed millions of wild birds and caused significant drops in the global population of some species. It has also spread into wild and domestic mammals, with various species of seals particularly affected. How it spreads Part of the challenge in controlling HPAI H5N1 is that it can spread through a wide range of transmission pathways. For example, the virus typically spreads through faeces, especially when in water. Imagine infected ducks in a pond, where the pond water acts as a conduit to infecting other ducks which are feeding or cleaning themselves. It can also be spread through direct contact and aerosol transmission, particularly in poultry farms. And it is spread through predation and scavenging, where animals like foxes maybe eat the carcasses of infected birds they find. While it has so far been found in more than 400 different bird species, the spread of HPAI H5N1 in the northern hemisphere is facilitated by freshwater dabbling ducks. Dabbling duck species feed predominantly at the surface of the water, sometimes even grazing on land. Importantly, ducks have very limited signs of disease when infected with HPAI H5N1, and appear to be able to continue to migrate while infected, allowing them to potentially spread the virus long distances. Overall, this virus has been devastating for wild birds. For example, 33–47 per cent of all adult northern gannets died in 2022 due to HPAI H5N1. On subantarctic Heard Island, 13,000 baby southern elephant seals died due to HPAI during the 2025–26 summer. The core dangers
The virus poses severe threats to ecology, agriculture, and potentially human health:
Ecological catastrophe: Experts fear the virus could decimate Australia’s vulnerable, unique wildlife. Globally, this strain has killed millions of wild birds and marine mammals. An earlier detection in late 2025 on Australia’s remote sub-Antarctic Heard Island wiped out over 13,000 elephant seal pups.
Agricultural disruption: Though H5N1 has not yet entered Australia’s commercial poultry or egg systems, any future spread would necessitate mass culls, threatening farming businesses and driving up food prices.
Human health risks: While human infections remain rare and there is limited evidence of human-to-human transmission, exposure can cause severe respiratory disease or death. Globally, out of nearly 1,000 human H5 cases reported to the World Health Organization (WHO) since 2003, roughly half were fatal