Flu overtakes Covid as leading respiratory killer ahead of winter season

Australia heads into winter with respiratory virus numbers lower than last year, but leading health experts warn the country should not become complacent after the deadliest flu season of this century.

The 2026 flu season is unpredictable, vaccination rates are still lagging behind and last year’s unusually long flu season could provide clues about what lies ahead, experts said at a national science briefing on Tuesday.

More than 1700 Australians will die from flu in 2025; this was the highest annual flu death toll recorded this century.

Early symptoms

Australian Center for Disease Control deputy director-general Masha Somi said the first months of 2026 were off to a quieter start than last year in terms of flu, Covid-19 and RSV.

“More than 29,300 cases of influenza have been reported so far this year, which is approximately half the number seen at the same time in 2025,” Dr Somi said.

Covid cases have also decreased, with 31,000 infections reported in 2026; This is roughly half of last year’s preliminary figures.

RSV notifications follow a similar trend; It remains 16 percent lower than the same period in 2025 and is “currently declining slightly nationally after a steady increase throughout February and March.”

Despite the promising start, experts emphasized that winter is not yet here and flu season traditionally peaks in the colder months.

Flu left Covid behind

One of the most striking changes to emerge from the briefing was the changing pattern of respiratory deaths in Australia.

“Since August 2025, the number of deaths due to influenza is higher compared to Covid-19,” Dr Somi said.

Covid was the leading cause of death from acute respiratory infections from 2020 to mid-2025.

The spike in flu deaths was linked to last year’s large case numbers rather than evidence of a more severe virus.

“Other surveillance systems have not shown circulating flu to be more severe in 2025 than in previous years,” he said.

Why was last year’s flu season unusual?

Professor Patrick Reading of the Doherty Institute said the 2025 season stood out for both its scale and length.

Australia had “the highest number of deaths, the highest number of cases” and a long season that stretched into spring.

“We saw the emergence and dominance of a different subtype starting in September and October, and that was quite unusual,” he said.

The late-season surge was triggered by a strain known as H3N2 subclade K, which subsequently dominated the northern hemisphere winter and contributed to a “long, drawn-out” 2025 season.

Globally, influenza activity has remained high in recent months, especially during the winter season in the northern hemisphere.

However, current Australian flu activity remains low for now.

“Levels are really low but we expect to see an increase as we get into winter,” Professor Reading said.

Hospital tension and low vaccine uptake

Hospital surveillance data highlight the burden of influenza on families and the healthcare system.

Since 2022, more than 10,000 families across 21 hospitals have been affected by their child’s hospitalization, with more than six percent admitted to intensive care.

“You wouldn’t think your healthy five-year-old would be at risk of being hospitalized with flu, but they are,” Professor Macartney said.

Despite the risks, vaccine coverage is declining, especially among children and working-age adults.

“Of the youngest children funded for flu vaccination, only a quarter received the vaccine.

“Only three in ten working-age adults… have received a flu vaccine.”

Among Australians over 65, nearly six in 10 will be vaccinated in 2025, leaving four in 10 unprotected.

“You can cut your chances of being hospitalized for flu by half by getting vaccinated,” he said.

Experts emphasized that vaccination remains the most effective way to reduce hospitalizations, deaths and pressure on the healthcare system.

“Vaccination may not always completely prevent people from getting the infection,” Dr Somi said.

“But it reduces the severity of the disease and the likelihood of complications, hospitalization and death.”

Updated vaccines target possible variants

The flu 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 better suit the viruses we expect to be circulating during the winter months,” Professor Reading said.

The vaccine was designed months in advance using global surveillance data to predict which strains were most likely to be circulating.

“We cannot predict the severity or which virus or viruses will dominate in the next flu season. In a sense, we have to wait and watch,” he said.

Healthy people may still be at risk

Professor Kristine Macartney, of the National Center for Immunization Research and Surveillance, warned that flu was often underestimated.

“It can cause serious illness, it can result in hospitalization, it can result in death. This can happen in perfectly healthy people of all ages,” Professor Macartney said.

“The groups most at risk are the elderly, infants, young children, Aboriginal and Torres Strait Islander people and those with chronic conditions.”

He said many people still misunderstand how severe the flu can be.

“People always say: ‘I had no idea the flu could be this bad.’ “But when we encounter them, we see the true cost of the flu,” he said.