It’s likely the coming winter will be a bad flu season, following from a big increase in influenza cases over summer and autumn.
There have already been 40,000 confirmed cases of influenza in 2019, about three times the usual number recorded at this time of year.
Professor William Rawlinson said the number of cases could end up being the highest since 2017, when a quarter of a million laboratory-confirmed cases were recorded.
The laboratory numbers do not reflect the full extent of the flu, as most people do not get tested.
Prof Rawlinson said about two million people will be infected with the flu in a busy year, although only about a quarter or less are actually measured because most people do not get tested.
"I would predict a couple of million this year," he said on Tuesday.
"It's likely this will be the highest number since 2017 although I'd be very concerned that it may be higher because we haven't seen so much in 2018."
Experts expect there will be about 4000 deaths due to complications to do with the flu.
Immunisation Coalition chairman Professor Robert Booy said the actual number of deaths on average each season was about 3000 to 4000.
"I'm not saying we're getting more deaths this year than any other year," he said.
"We've got a very busy early season but it's nothing like the peak that we had in 2017."