Highly transmissible flu strain infects more than 2,500 Australians

More than 2,500 Australians have been reported infected with a highly transmissible H3N2 subclade called Super-K, and health authorities have issued national alerts as cases continue; next steps are undetermined at this time.

More than 2,500 infections have been reported in Australia in early January linked to a mutation of Influenza A (H3N2) known as subclade K, or Super-K. Scientists first identified the strain in September and health authorities issued national alerts in December. Officials say genetic changes appear to have made the virus more efficient at spreading but do not indicate increased severity compared with other H3N2 strains. Vaccination rates among some vulnerable groups were reported to have declined in 2025. Key points: - Over 2,500 confirmed infections in Australia in early January have been linked to H3N2 subclade K ('Super-K'). - Authorities reported Super-K spreads more readily but does not appear more severe; an Australian Health Protection Committee alert was issued on 12 December. - Reported vaccination rates in 2025 fell to 25.7% for children aged six months to five years and to 60.5% for people over 65; surveillance and alerts remain in place. Summary: Officials warned that the unseasonal persistence and rapid spread of Super-K could place pressure on health services during the holiday period, and national surveillance and alerts have been raised. Undetermined at this time.