Emergency rooms across Australia have been inundated with children struggling to breathe - and it's not because of COVID-19.

Respiratory viruses, including respiratory syncytial virus and influenza, have been hitting kids more frequently and in patterns not before seen.

According to Perth paediatrician Asha Bowen, Western Australia and the Northern Territory are experiencing a peak in RSV cases - something that would usually happen in June.

But during the pandemic, RSV surprisingly peaked nationally in January and February.

For RSV to climax in September and October, it gives hope that things are moving back to normal and towards the depths of winter - but it's anyone's guess if that is actually going to happen, Dr Bowen said.

The days of regular peaks and troughs are gone, with practitioners noticing numerous changes in the way viruses are presenting.

Couple that with limited immunity, thanks to spending months indoors during the pandemic, and children seem to be getting more of the viruses out there.

"Normally we see RSV and then influenza and then the other spring viruses like rhinovirus, metapneumovirus and others," Dr Bowen told AAP.

"But there has been no sort of usual pattern this year ... they are cropping up whenever now and maybe it is because COVID has left them room.

"We found COVID had its peak nationwide in January and February and then the other viruses came."

She said the increased number of respiratory illnesses in children meant an increase in hospital presentations and added pressure on the system.

Royal Australasian College of Physicians president and paediatrician Jacqueline Small said it had been a tough winter for all but especially children.

"Now we've entered spring, we're hoping for a reprieve from the volume of viruses circulating in the community," she said.

"We must remain vigilant and remember we can always do more to protect ourselves and our children, such as keeping up good hygiene and staying home if you're sick."

Victoria's Deputy Chief Health Officer Associate Professor Deborah Friedman said high vaccination numbers helped reduce flu infections in 2022.

She said the flu season was early, short and sharp in Victoria but more cases may emerge later this year when holiday-makers return from overseas.

Influenza peaked in Victoria with about 18,000 cases in May and declined to 350 in August.

It was overtaken by the number of notified cases of RSV in mid-June.

RSV mostly affects younger children, with 42 per cent of cases notified in 2022 aged under three.

The number of people presenting to emergency departments with respiratory illnesses other than COVID-19 and asthma increased over the winter months, with children under five making up an increased proportion.

Medical director of infection prevention and epidemiology at Monash Health, Professor Rhonda Stuart, said everyone was catching up on viruses they didn't get during the pandemic.

There was hardly any influenza and very few other respiratory viruses in 2020 and 2021.

"It's not necessarily immunity," she said.

"These viruses often like to transmit in the winter because we're all indoors and we don't physically separate so much, and it's much easier to transmit during the winter months.

"But as spring comes and the doors open, and we have good ventilation, and people are outdoors, respiratory viruses and COVID won't transmit nearly as easily."

The Department of Health and Aged Care said COVID-19 testing likely had an effect on identifying the number of people with respiratory viruses but it was unable to quantify those statistics as the data was de-identified.