A potential first mass mortality event from H5N1 bird flu has been detected in Australia, marking a significant escalation of the disease’s spread across the continent. Helicopter surveillance revealed 49 dead greater crested terns and 35 additional sick terns on Baudin Rocks near Robe in South Australia on Saturday. South Australia’s chief veterinarian characterized the finding as the likely first mass mortality occurrence linked to the disease in the country.
The outbreak is spreading beyond initial coastal detections. Additional cases have been identified in greater crested terns inland at Monarto, where several poultry operations are located. Three silver gulls have also tested positive for the virus, following confirmation of another silver gull case earlier in the week. The appearance of cases in multiple bird species and across diverse geographic locations suggests the disease is establishing itself in Australian wildlife populations.
Experts expressed concern about the rapid progression and potential for continued escalation. Case numbers increased by 20 within a few days, bringing the total confirmed detections to 53. Victoria confirmed its first cases this week, joining Western Australia, South Australia, New South Wales, and Queensland in recording positive detections. Victorian authorities reported preliminary positive results from five additional crested tern samples sent for testing.
Conservation officials emphasized the particular risk posed by silver gulls, which are highly abundant, widely distributed, and engage in scavenging behaviors that facilitate disease transmission. These birds also frequent water bodies and coastal areas known as breeding grounds for the virus, potentially enabling spread to inland regions and urban bird populations. Five confirmed cases at Seal Bay on Kangaroo Island raised additional concerns regarding transmission to the area’s endangered Australian sea lion population.
Authorities indicated that disease control measures were limited, with surveillance efforts representing the primary response strategy. Conservation experts likened the emerging situation to patterns observed in South America, where early detections were followed by rapid escalation and mass mortality events. Officials cautioned that the situation remained in early stages, with significant uncertainty regarding the susceptibility of Australia’s unique native bird species to the virus.
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