More than 2,500 Australians have been infected with a highly transmissible new flu strain, Super-K, in the first week of January, raising concerns of a record flu season. The strain, a mutation of Influenza A H3N2 known as subclade K, was first identified in September by scientists at the Peter Doherty Institute for Infection and Immunity in Melbourne.
Health authorities stress that Super-K does not appear to cause more severe illness than previous strains, but its genetic changes enable rapid spread. Vaccines remain effective against severe disease, with EU research showing 72.8% effectiveness in preventing hospitalisation for children and 66.3% for adults aged 18-64, though effectiveness drops to 31.7% for those over 65.
Vaccination rates have fallen sharply among vulnerable groups. In 2025, only 25.7% of children aged six months to five years were vaccinated, the lowest since 2021, while rates for over-65s slipped to 60.5%, a five-year low, according to the Royal Australian College of General Practitioners.
New South Wales has reported over a third of recent cases, with emergency department visits for flu-like illness spiking to more than 370 per week by mid-November. The Australian Health Protection Committee warned that the unseasonable persistence of the virus could strain healthcare resources over the holiday period.
Prof Ian Barr, deputy director of the WHO Collaborating Centre for Reference and Research on Influenza, noted that Super-K originated in the US in mid-2025 and began appearing in Australia in August. He described it as a “very fit virus” that continues to spread even in January, when flu typically subsides.
Health authorities urge Australians, especially those travelling to the northern hemisphere, to get vaccinated. The Australian Centre for Disease Control confirmed that current case numbers are higher than usual for this time of year.
