More Australians have been diagnosed with the flu in the first five months of 2015 than in any previous year.

However while the government’s Australian Influenza Surveillance Report shows case numbers between January and May have reached their highest levels since records began in 2001, the health department says in the report that overall influenza activity as low and stable.

The Australian flu season is considered to be between June and October.

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Meanwhile, a one-shot flu jab for life may be on the way after a scientific breakthrough made by an Australian-led research team.

The scientists have discovered how flu-killing cells memorise strains of influenza and destroy them.

The teams from the University of Melbourne and Shanghai’s Fudan University worked together during the first outbreak of avian flu in China in 2013.

University of Melbourne’s associate professor Katherine Kedzierska says 99 per cent of people with the H7N9 virus were hospitalised, while 30 per cent died.

“After collecting samples from infected patients, we found that people who couldn’t make these T-cell flu assassins were dying,” she said.

“These findings lead to the potential of moving from vaccines for specific influenza strains toward developing a protection which is based on T-cells.”

She described the cells as the body’s “army of hitmen”, tasked with eliminating the virus-infected cells.

The researchers want to make a vaccine from a component of the early killer T-cells.

The breakthrough could lead to the development of a vaccine component that can protect against all new influenza viruses.

It also could lead to a one-off universal flu vaccine shot, Prof Kedzierska said.

“This work will also help clinicians to make early predictions of how well a patient’s immune system will respond to viruses, so they can manage early interventions such as artificial ventilation more effectively,” she said.

The findings are published in the journal Nature Communications.