Health economist Martin Hensher, who has led a Deakin University team studying long COVID, does not want to be alarmist, but said there remained much unknown about long-term effects and complexities in what COVID-19 served up post-infection.

Long COVID from the virus' omicron cases was about to emerge in Ballarat from now, the University of Tasmania professor predicted. The city is about three or four months into the omicron wave, which picked up momentum in the Christmas-New Year period.

Last night Victoria's pandemic declaration was extended for three months amid rising COVID-19 cases across the state.

In a government statement released on Wednesday night, Premier Daniel Andrews said he was satisfied COVID-19 still posed a serious risk to public health.

The extension will start from 11.59pm on April 12 and last through to July 12.

"This extension enables us to keep modest and sensible settings in place to reduce transmission and hospitalisation," Mr Andrews said in the statement.

How and exactly what long COVID presents remains contentious in nations that have spent longer with the virus and its variants. Predominantly people experience fatigue.

Professor Hensher said vaccination, while it did not guarantee against infection, it did halve a person's chance for long COVID.

The best defence, he said, was to try and avoid risking your chances altogether.

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Professor Hensher said complacency - including from those who had already been infected - was not an excuse. This was not about lockdowns or tougher restrictions. This was about being sensible, masking up, being vaccinated and socialising in well-ventilated or outdoor settings. Even in winter.

"We've all got to acknowledge that even if we're frustrated and tired, it doesn't change the biology of how the virus works," he said.

This is a message also made clear by Deakin University epidemiologist Catherine Bennett, who warned Australia's influenza levels had already exceeded last year's case numbers alone about March. The two viruses circulating together signalled a long winter ahead.

Ballarat COVID-19 active cases have remained stubbornly above 1000 the past week with rising known new infections each day. This included 1100 new cases recorded in Ballarat on Wednesday.

Professor Bennett said the northern hemisphere presented "twin peaks" in COVID-19 and influenza, the latter slowing when the other dropped. This, coupled with no certainty in which COVID-19 variant a person contracts, made it hard to gauge exactly what we would be facing this winter.

"It is harder to avoid getting infected now [with COVID-19], transmission rates are high, but that doesn't mean we stop trying to avoid it," Professor Bennett said.

"People might think 'I'm not going to get severe disease to end up in hospital'. Most don't. But you don't need severe disease to get long COVID. If it doesn't go away - the headaches, the foggy feeling - the malaise is very different. Some people are losing a sense of taste or smell and that's awful.

"If you can't avoid people completely, such as a busy supermarket, even if it is not a rule, wear a mask...All the things we've talked about, like vaccinations matter, so if you have a mask and it doesn't worry you wearing it, put it on. Colds, flu and COVID-19 - it makes it a little harder for you to catch."

Grampians Public Health Unit infectious disease doctor Aaron Bloch said it was hard to gauge people presenting to Grampians Health with long COVID.

Dr Bloch said it was most likely people with long COVID symptoms would visit their general practitioner. He added Ballarat's high vaccination rates set the city in good stead for preventing lingering effects.

Dr Bloch warned against relying on immunity from having had the virus.

"Unfortunately, we know now definitively that you can be reinfected," Dr Bloch said. "You will get some protection post infection for weeks to several months, but after that, it drops.

"We are all - including health care workers - sick of COVID. But the best way to effectively live with COVID is not to pretend it doesn't exist. Rather, we need to maximise our enjoyment of the important things in our life - cherished time with family, work, fun social activities - while minimising the risk of acute and long COVID...It's also critical to avoid our friends, loved ones and vulnerable or high risk settings when we have any respiratory symptoms.

"This is important even if your COVID test is negative."

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