What We Know About Australia’s Bird Flu, Which Has Crossed Over to Mammals

What We Know About Australia’s Bird Flu, Which Has Crossed Over to Mammals By Emma Clarke, BBC News Date: 25 August 2026 Australia confirmed its first case of the highly pathogenic avian influenza H5N1 in June, when a flock of migratory seabirds on the southern coast tested positive. The discovery, made by the Commonwealth Scientific and Industrial Research Organisation (CSIRO), triggered an immediate lockdown of several nature reserves and a rapid mobilisation of veterinary and biosecurity teams. At the time, officials stressed that the virus was confined to wild birds, but the situation has since escalated, with new findings indicating that the pathogen has jumped to mammals, raising concerns about a broader public‑health threat..

The initial outbreak was traced to the short‑tailed shearwater, a seabird that migrates annually between Australia and the Arctic. Genetic sequencing of the virus revealed a clade 2.3.4.4b strain, closely related to the Eurasian lineage that has caused repeated outbreaks across Europe and Asia in recent years. Researchers at the University of Queensland noted that the virus carried mutations associated with increased transmissibility among birds, suggesting it could spread more readily through dense breeding colonies..

Within weeks, additional positive samples were recorded in silver gulls and black‑tailed godwits along the coastline of New South Wales and Victoria. State governments responded by imposing emergency wildlife protection orders, banning the collection of eggs and the handling of dead birds, and deploying teams to incinerate contaminated carcasses. The Australian Department of Agriculture, Water and the Environment (DAWE) allocated an extra $45 million in emergency funds to support surveillance, testing and biosecurity measures in farms and wildlife habitats..

However, critics argue that the response was hampered by limited laboratory capacity and a shortage of personal protective equipment for field workers, especially in remote coastal regions. Complicating matters further, in late July a dead feral cat was found on a farm near Mildura, Victoria, testing positive for the same H5N1 strain. Subsequent necropsies confirmed the presence of the virus in the cat’s lung tissue, marking the first recorded mammalian infection on the Australian mainland..

The cat is believed to have contracted the virus after feeding on infected bird carcasses, a route that mirrors similar spill‑over events documented in Europe and North America. This development prompted the National Health and Medical Research Council (NHMRC) to issue a warning to veterinarians and pet owners about the potential risks of transmission. The detection of H5N1 in mammals ignited a flurry of activity among epidemiologists, who began modelling the likelihood of sustained mammal‑to‑mammal spread..

Preliminary models from the Australian Centre for Disease Preparedness suggest that, while the current risk of human infection remains low, the virus’s ability to adapt to mammalian hosts could increase its pandemic potential if it acquires additional mutations. The models also highlight that feral cats, foxes and possums, all of which frequently scavenge on bird remains, could act as bridging species, facilitating further spread into urban environments. In response, the federal government announced a nationwide surveillance programme targeting both wildlife and domestic animals..

Veterinarians are now required to report any unexplained deaths in mammals, and a new rapid‑test kit has been rolled out to abattoirs and veterinary clinics across the country. The programme also includes a public‑awareness campaign, urging residents to avoid handling dead birds and to report sightings of sick wildlife to the Department of Agriculture hotline. Despite these measures, compliance has been uneven, particularly in remote Aboriginal communities where traditional hunting practices intersect with biosecurity guidelines..

Industry stakeholders, especially poultry producers, have expressed alarm at the prospect of a virus that can jump species. The Australian Chicken Meat Federation has called for stricter quarantine protocols and compensation schemes for farms forced to cull flocks. In early August, a commercial layer farm in South Australia reported a sudden increase in mortality among its birds, prompting an emergency test that returned a positive H5N1 result..

The farm was subsequently depopulated, and the surrounding area was sealed off for a three‑week decontamination period, costing the owners an estimated $12 million. Scientists are now racing to determine whether the virus is mutating within Australian hosts. Samples collected from infected mammals are being analysed for the PB2 E627K mutation, a change known to enhance replication in mammals..

To date, only a single sample has shown this mutation, but its presence underscores the need for vigilant genomic surveillance. The CSIRO’s Avian Influenza Reference Laboratory has increased its sequencing capacity to 500 genomes per week, a ten‑fold rise from pre‑outbreak levels, aiming to track the virus’s evolutionary trajectory in real time. Internationally, Australia’s situation is being watched closely by the World Health Organization (WHO) and the Food and Agriculture Organization (FAO)..

Both agencies have offered technical assistance, and the WHO has placed Australia under a “moderate risk” category for potential human cases. In a recent briefing, WHO spokesperson Dr Maria Van Kerkhove warned that while human infections remain rare, the global community must be prepared for the possibility of a new zoonotic wave, especially if the virus establishes a foothold in mammals that interact with people. Public health officials have reiterated that the risk to the general population is still minimal, noting that H5N1 does not spread easily between humans without close, prolonged contact..

Nonetheless, they have advised individuals with flu‑like symptoms who have been to sick or dead birds to seek medical assessment promptly..