Australia has confirmed its first suspected case of highly pathogenic avian influenza (HPAI) H5N1 in a brown skua found in Cape Le Grand National Park near Esperance, Western Australia. The virus, specifically the clade 2.3.4.4b lineage, was also suspected in a southern giant petrel from the same area. Samples have been sent to the CSIRO for confirmation.
Origin and Evolution of H5N1
Avian influenza viruses have existed for millennia, typically causing no disease in birds. However, in 1996, one strain evolved into HPAI H5N1, causing severe disease in poultry. With chickens now comprising about 70% of all birds worldwide, they serve as a critical reservoir for the virus's ongoing evolution.
Since 2021, HPAI H5N1 has triggered a global animal pandemic, devastating wildlife across continents. It has killed millions of wild birds and significantly reduced populations of some species. The virus has also spread to wild and domestic mammals, particularly affecting seals.
Transmission Pathways
The virus spreads through multiple routes: feces (especially in water), direct contact, aerosol transmission in poultry farms, and predation or scavenging of infected carcasses. Over 400 bird species have been affected. In the northern hemisphere, freshwater dabbling ducks facilitate spread because they show limited disease signs and can migrate while infected, carrying the virus long distances.
For example, 33–47% of adult northern gannets died in 2022 due to H5N1. On subantarctic Heard Island, 13,000 baby southern elephant seals died during the 2025–26 summer.
Core Dangers
The virus poses severe threats to ecology, agriculture, and human health:
- Ecological catastrophe: Experts fear decimation of Australia's unique wildlife. Globally, millions of wild birds and marine mammals have died.
- Agricultural disruption: Although H5N1 has not entered Australia's commercial poultry or egg systems, future spread could necessitate mass culls, threatening farming businesses and raising food prices.
- Human health risks: Human infections are rare, with limited human-to-human transmission, but exposure can cause severe respiratory disease or death. According to the World Health Organization, nearly 1,000 human H5 cases have been reported since 2003, with roughly half fatal.
