A Victorian child has died during an outbreak of influenza over the summer season.

Deputy Chief Health Officer Dr Brett Sutton confirmed cases of summer flu are significantly higher than the same time last year, with more than 2800.

"It's certainly more than double statewide, this year, and there'll be a lot more out there that haven't been diagnosed," Dr Sutton told 3AW radio.

More than 2800 cases of influenza were recorded over the summer season, in increase in numbers from the same time last year. (AAP)

"It's definitely one of the biggest summer seasons we've seen.

"It is unusual for children to die, it's a relatively rare thing. But it's a reminder to all of us we're not just protecting ourselves when we get the vaccine, we're helping to protect those who are at risk, including children."

The Metropolitan Remand Centre has also had a flu outbreak, with those affected advised to be in isolation until the infection passes.

Dr Sutton said the higher number of cases could be related to international travel, greater reporting and more doctors conducting tests.

While anyone is vulnerable, the elderly, pregnant women and children are most at risk.

"We've always emphasised the dangers of flu - that's why we've always pushed the vaccination and other measures people can take to stay away from others when they're unwell, to make sure they don't go to work, to make sure they wash their hands, to cough into their elbow," he said.

While people can be infected any time of year, the season officially begins in April and people are advised to get the flu vaccine from mid-April onwards.