Winter is over but cases of influenza are surging in Australia, with health experts warning that the risk of infection is now at its highest as the late flu season nears its peak. In the fortnight ending 6 September, the Australian Respiratory Surveillance report recorded 31,650 notified influenza cases , up 27.2% from the previous period. That included 14,256 cases in New South Wales , followed by 7,039 in Victoria and 6,625 in Queensland.
Sign up for the Breaking News Australia email In Victoria , influenza notifications have increased by about 400% over the past seven weeks, with influenza A accounting for the majority of cases. Emergency department presentations for acute respiratory infections have risen by 25% in Victoria over the past six weeks, primarily driven by children aged 5 to 17 years. The state’s chief health officer, Dr Caroline McElnay, said the flu season “has arrived later than in previous years, with cases continuing to rise as we move into spring”.
McElnay said cases were expected to remain high over the coming weeks, including through the school holidays. She said people could “protect themselves and their loved ones these school holidays by staying home when sick, keeping unwell children at home, and reminding everyone that it’s not too late to get a flu vaccine”. Why is this flu season so late and when will it peak?
Dr James McCaw, an epidemiologist at the University of Melbourne’s Infectious Disease Dynamics Unit, confirmed the timing of the 2026 flu season was “definitely late” compared with typical winter peaks. There have been 130,355 influenza cases recorded so far in 2026 – 62.6% fewer than at the same time in 2025. Chart showing reports of respiratory illness “We don’t understand enough about influenza biology and epidemiology to know exactly why that might be the case.
It’s unusual, but ... it doesn’t make it more severe or more mild, it’s just late,” McCaw said. Queensland’s chief health officer, Dr Marianne Gale, said this “more unusual flu season” may be due to last year’s record cases. “In addition to that, we also had a second wave of the ‘Super-K’ strain from Europe throughout December and January,” she said in a statement last month.
“These factors change the population’s immunity to flu, which is likely why we’re seeing a different looking flu season this year.” Prof Patrick Redding, the director of the WHO Collaborating Centre at the Doherty Institute, said that late-season surges could be influenced by shifting weather patterns, dry air, increased indoor socialising and “patchy” influenza vaccine uptake affecting community immunity. Because overall vaccine uptake has remained low across working-age adults and school-age children, significant areas of susceptible populations remain. Which strains of flu are driving cases?
Influenza B has remained at very low levels all year, McCaw said, leaving influenza A ( H3N2 ) as the driver of the current surge in notifications. While A(H3N2) is now plateauing, a secondary wave of influenza A(H1N1) is now driving case increases in Victoria and New South Wales. Will getting vaccinated help?
The flu season is “near the peak, so now is your highest risk period”, McCaw said. As the virus continues to spread, health experts advise that getting vaccinated is the most effective way to prevent severe illness and ease pressure on hospital emergency departments. “If you haven’t had the influenza vaccine, now is a great time to get it because it is effective at reducing your chance of showing symptoms and feeling very unwell,” McCaw said.
With national uptake of the flu vaccine sitting at just 30.2%, Redding also urged unvaccinated Australians to book an appointment. This year’s jab is a strong match for circulating strains, with immunisation yielding an estimated 35% reduction in flu hospitalisations, he said.
Source: The Guardian
