Influenza cases all but disappeared as Australia bunkered down during the first two years of the COVID-19 pandemic.
But as the country opens up again to international travellers, doctors are getting ready for the return of the flu.
Professor Ian Barr is the deputy director of the World Health Organisation (WHO) Collaborating Centre for Reference and Research on Influenza.
"I think in 2022 we'll see the return of influenza," he told SBS News.
"The only question is how severe the season will be, and that's difficult to judge. I don't think we're going to have a big year like 2017 or 2019, but we will see a low-to-moderate year I think."
Influenza outbreaks have recently been reported in both Fiji and New Caledonia, while Denmark has also recorded a sharp increase in flu cases.
Australia’s strict COVID-19 lockdowns and closed borders have drastically curbed the spread of influenza in the past two years.
In 2019, before international travel ground to a halt, Australia suffered one of its worst flu seasons on record - with more than 313,000 lab-confirmed cases and 953 flu-associated deaths.
By comparison, in 2021 when lockdowns were in full effect, there were just 598 flu cases and zero flu-linked deaths.
The Victorian Infectious Diseases Reference Laboratory studies different strains of influenza collected from Australia, New Zealand, and further abroad.
Australia's strict COVID-19 restrictions helped to stem the spread of influenza. Source: AAP / AAP Image/Dan Himbrechts
Professor Barr said flu surveillance information collected by these centres was used to design vaccines targeting the strains most likely to emerge over winter.
"That involves isolating viruses, growing viruses, and then purifying and inactivating the viruses," he said.
"We make decisions around six-to-nine months before the viruses actually circulate, and make those available to manufacturers who scale up production and make vaccines."
Natural immunity to the influenza virus has likely weakened without being regularly exposed over winter.
Doherty Institute infectious diseases expert Dr Kudzai Kanhutu said it was difficult to tell when flu cases might spike.
"It was always a bit of a worry for all of us who work in infectious diseases, when we had no cases coming into the hospital for the past two years," she told SBS News.
"We're not too far away from an epic flu season, but when it comes, nobody knows."
Dr Kanhutu said particularly vulnerable groups included the elderly, the really young, pregnant women, and those with compromised immune systems.
She said the best way to protect yourself against the flu was still through vaccination.
This year’s flu vaccine is already starting to arrive at some GPs and pharmacies, but Sydney GP Dr Danielle McMullen suggested waiting until April, if possible, to give the best protection through the winter months.
"Our medical advice is that timing the vaccine starting from the end of April tends to give you the best coverage through our predicted flu season," said Dr McMullen, who is the NSW president of the Australian Medical Association.
"It's not one where you need to rush out today and have it, we probably recommend having that in mid-to-late April. The one caveat is when you need it for travel."
Flu vaccines are free for children between 6 months and 5 years old, as well as pregnant women and over 65s.
The government has said it is safe to pair the flu vaccine with the COVID-19 booster jab.
