The national Flutracking site shows 47 cases of influenza were reported in Warrnambool in the week ending May 15.

There were 15 cases in Port Fairy, 13 in Portland, six in Terang and five in Mailors Flat.

The interactive map only lists cases of the flu that are reported by those who use the website.

Deakin University epidemiologist Catherine Bennett said the flu season had kicked-off last month despite northern strains of influenza usually taking off in late May.

"The flu season started early in 2019 and we're seeing it happen again," she said.

"It tends to be associated with a bigger flu season as more influenza circulating in the northern hemisphere starts travelling south and getting here earlier."

But Professor Bennett said there was nothing pointing to a "worse" flu season.

She said a vast majority of Australians had steered clear of influenza during the pandemic as they actively avoided COVID-19.

"This is relevant in that you forget how bad things are when you don't have to deal with them year in, year out," Professor Bennett said.

She said it also meant people were less protected against infection.

"That means partial cross-immunity across the years is diminished in most of us because we haven't come across the flu in two winters," Professor Bennett said.

"Instead of being a six-month break from last time you might have seen the flu, it's two-and-a-half years. That's four times the gap and that's the difference, we don't have the same protection.

"Previously you might fight an infection or have such a mild infection you don't even know it. Usually our immune system is boosting all the time but we just haven't had those infections."

Professor Bennett said the rate of influenza decreased substantially during the pandemic when international borders closed.

She said people were now also facing the "double whammy" of the flu and COVID-19.

"The message is - don't wait for your flu shot, get it now," she said.

Flu vaccinations are available at pharmacies and GPs and are free for those with increased risk of complications, including children aged six months to less than five years, Aboriginal and Torres Strait Islander people, pregnant women, people aged over 65 and those with medical conditions.

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