Australia is heading into winter with respiratory virus numbers currently lower than last year, but leading health experts warn the country should not get complacent after the deadliest flu season this century.
At a national science briefing on Tuesday, specialists said the 2026 flu season remained unpredictable, vaccination rates were still lagging, and last year’s unusually long influenza season could offer clues about what lay ahead.
More than 1700 Australians died from influenza in 2025, the highest annual flu death toll recorded this century.
Early signs
Australian Centre for Disease Control acting deputy director-general Masha Somi said the first months of 2026 showed a quieter start than last year across influenza, Covid-19 and RSV.
“So far this year, more than 29,300 influenza cases have been reported, about half the number seen at the same time in 2025,” Dr Somi said.
Covid cases are also down, with 31,000 infections reported in 2026 — roughly half of last year’s early numbers.
RSV notifications are following a similar trend, sitting 16 per cent lower than the same period in 2025 and “currently decreasing slightly after a steady increase through February and March nationally”.
Despite the encouraging start, experts stressed winter has not yet arrived, and flu season traditionally peaks in the colder months.
Flu overtakes Covid
One of the most striking shifts revealed in the briefing was the changing pattern of respiratory deaths in Australia.
“Since August 2025, there have been more deaths involving the flu … compared with Covid-19,” Dr Somi said.
Covid had been the leading cause of death from acute respiratory infections from 2020 until mid-2025.
The spike in flu deaths was linked to last year’s massive case numbers rather than evidence of a more severe virus.
“Other surveillance systems didn’t indicate that the influenza that was circulating was more severe in 2025 than in previous years,” she said.
Why last year’s flu season was unusual
Professor Patrick Reading from the Doherty Institute said the 2025 season stood out for both its scale and its length.
Australia experienced “the highest number of deaths, the highest numbers of cases” and an extended season that ran well into spring.
“What happened from September and October onwards is we saw an emergence and a dominance of a different subtype, and this was quite unusual,” he said.
The late-season surge was driven by a strain known as H3N2 subclade K, which later dominated the northern hemisphere winter and contributed to a “long and extended” 2025 season.
Globally, influenza activity has remained high in recent months, particularly during the northern hemisphere winter.
However, current Australian flu activity remains low, for now.
“Levels are really low but we’re expecting to see an increase quite soon as we move into winter,” Professor Reading said.
Hospital strain and low vaccine uptake
Hospital surveillance data highlights the burden influenza places on families and the health system.
Across 21 hospitals, more than 10,000 families have been impacted by the hospitalisation of their child since 2022, with more than six per cent admitted to intensive care.
“You don’t think of your healthy five-year-old as being at risk of hospitalisation for influenza, but they are,” Professor Macartney said.
Despite the risks, vaccination coverage is falling, especially among children and working-age adults.
“In the youngest children who are funded for influenza vaccine … only one in four took up the vaccine.
“Only three out of ten working-age adults … took up a flu vaccine.”
Among Australians aged over 65, about six in 10 were vaccinated in 2025, leaving four in 10 without protection.
“You can halve your chance of being hospitalised from influenza by having a vaccine,” she said.
Experts stressed vaccination remained the most effective way to reduce hospitalisations, deaths and pressure on the health system.
“Vaccination might not always stop people from catching an infection entirely,” Dr Somi said.
“However, it does reduce the severity of disease and the likelihood of complications, hospitalisations and death.”
Updated vaccines target likely strains
The influenza vaccine has been updated ahead of the 2026 season, with two of the three virus components changed.
“The H1N1 and H3N2 components of the vaccine … have been updated to provide a better match for the circulating viruses we’re expecting in our winter,” Professor Reading said.
The vaccine is designed months in advance using global surveillance data to anticipate which strains are most likely to circulate.
“We cannot predict the severity or which virus or viruses will predominate in the upcoming influenza season. We kind of have to wait and watch,” he said.
Healthy people can still be at risk
Professor Kristine Macartney, from the National Centre for Immunisation Research and Surveillance, warned influenza was often underestimated.
“It can cause serious illness, it can result in hospitalisation, it could result in death. This can happen in perfectly healthy people of all ages,” Professor Macartney said.
“The most at-risk groups are older people, infants, young children, Aboriginal and Torres Strait Islander people, and those with chronic conditions.”
She said many people still misunderstood how severe influenza could be.
“People always say, ‘I had no idea the flu could be that bad.’ But when it meets them … we see the real cost of influenza,” she said.
