It is associated with severe seasonal epidemics, high hospitalisations and deaths.
A deadly strain of influenza, H3N2, is quickly spreading and is expected to hit Australians hard this winter.
H3N2 is a subtype of flu that includes the emerging Super K variant and is most usually associated with severe seasonal epidemics, high hospitalisations and deaths.
Seasons dominated by the strain across the world have been characterised by higher death rates.
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The Australian Centre for Disease Control has recorded more than 32,500 laboratory-confirmed cases of the flu across the country so far this year.
It also found 75.6 per cent of flu viruses this season have been H3N2.
About 20 per cent of those are adults over the age of 65 - the most vulnerable group to H3N2.
Austin Health associate professor Michael Woodward said H3N2 seasons can be worse for older people as it can lead to hospitalisations and, in severe cases, death.
"Flu is sometimes dismissed as a bad cold, but for older adults it can be much more serious," he said.
"If H3N2 continues to dominate this season, people aged 65 and over should speak with their GP, pharmacist or healthcare professional about how they can help reduce their risk."
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Symptoms include high fever and chills, body aches, a dry and stubborn cough and headaches.
Woodward advised all Australians, particularly those who are older, to check if they are up to date with their vaccinations.
"It's not too late to discuss prevention," he said.
Vaccination rates have declined across the country.
Bupa found only about one-in-three Australians receive their flu shots, compared to more than half before the COVID-19 pandemic.
Low vaccination rates have contributed to the deadliest flu season in a decade after 1701 people died from influenza last year.
That was about 400 more deaths than the national road toll.
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