MELBOURNE, Jan. 3 (Xinhua) -- Australian scientists say the country's record-breaking 2025 flu season has triggered a fast-spreading "Super-K" strain now driving record global outbreaks.
The influenza A (H3N2) subclade K viruses were first detected in Australia and New Zealand in August, late winter, during an unusually long 2025 flu season that extended into summer, and have been identified in over 30 countries worldwide, said experts from Australia's Peter Doherty Institute for Infection and Immunity.
More than 427,000 influenza notifications were recorded in Australia's National Notifiable Diseases Surveillance System in 2025, about 21 percent more than in 2024, the highest since national reporting began in 2001, with 977 deaths in the first nine months of last year, official statistics showed.
"Subclade K viruses have 'drifted' to accumulate mutations in one of the surface spikes of the virus, known as the hemagglutinin, such that these viruses may be less well recognized by immune responses generated from previous infection or vaccination," said a release of the Doherty Institute in December 2025.
However, Australian hospital and general practice data indicate vaccination still roughly halves the risk of doctor visits and hospitalization for influenza.
"Even when influenza viruses drift, vaccines continue to reduce severe disease complications and death," said Harry Stannard, a medical scientist and PhD candidate at the Doherty Institute.
Australian experts have updated two of the three vaccine components for the 2026 Southern Hemisphere season, including the H3N2 component.
"It is always a bit of a race to update the vaccine to give it the best chance of inducing immune responses that provide effective protection during our influenza season next year," said Professor Patrick Reading, director of the World Health Organization Collaborating Center for Reference and Research on Influenza at the Doherty Institute.
Reading called for continued investment in surveillance, vaccines, and antivirals to reduce severe illness ahead of future flu seasons. ■
