A highly pathogenic strain of avian influenza has devastated a colony of Australian sea lions on Kangaroo Island, South Australia, killing an estimated 75 per cent of pups born this season. The outbreak, confirmed by the Australian Department of Agriculture, Fisheries and Forestry, has prompted British virologists to call for an urgent international inquiry into the spread of the H5N1 virus among marine mammals.
Preliminary reports from the University of Adelaide suggest that the H7N7 subtype – a variant previously circulated in poultry but not known to cause mass mortality in seals – has now adapted to mammalian hosts. Dr. James Morton, a veterinary epidemiologist at the University of Oxford, described the findings as “unprecedented” and warned that the virus could pose a threat to other marine species and potentially human populations.
“This is no longer a simple avian disease,” Dr. Morton said. “We are witnessing a jump across species barriers that should alarm public health authorities globally. The loss of such a high proportion of juvenile seals indicates a high case fatality rate and effective transmission within the seal colony.”
The outbreak was first detected in late July when park rangers observed unusually high numbers of dead pups on the island’s northern beaches. Laboratory tests confirmed the presence of H7N7 in tissue samples. Subsequent aerial surveys estimated that 3,000 of the estimated 4,000 pups born in the colony have died.
Australian authorities have implemented a culling program for infected birds in the vicinity and are monitoring the surviving seals for signs of illness. However, the remote location and limited veterinary resources have hampered containment efforts.
The British government’s Animal and Plant Health Agency has offered technical assistance, and a team of pathologists from the Pirbright Institute is expected to arrive on the island later this week. In a joint statement, the Royal Society for the Prevention of Cruelty to Animals and the World Wildlife Fund called for a coordinated international response to investigate the origins of the outbreak and assess the risk of zoonotic spillover.
“The rapid evolution of avian influenza viruses in wildlife underscores the need for a global surveillance network,” said Professor Sarah Gilbert, a senior researcher at the London School of Hygiene and Tropical Medicine. “We must understand how this virus crossed from birds to seals, and what mutations it may have acquired.”
Australia has reported sporadic cases of H5N1 in wild birds since 2023, but this is the first recorded mass mortality event among marine mammals in the region. The closest precedent occurred in 2014, when H10N7 killed thousands of harbour seals in northern Europe.
The commercial fishing industry, which relies on the health of the marine ecosystem, has expressed concern. The Australian Fishing Vessels Association has urged the government to declare a state of emergency to ensure adequate resources for containment and research.
Downing Street has not yet commented on the request for an inquiry, but the Chief Medical Officer for England, Sir Chris Whitty, has been briefed on the situation. British scientists emphasise that while the public health risk in the United Kingdom remains low, the episode is a stark reminder of the interconnectedness of wildlife and human health.
