Flu or COVID? CSIRO immunologist Dr Daniel Layton and RACGPs Dr Charlotte Hespe say taking a RAT test won't be accurate enough

CSIRO immunologist Dr Daniel Layton said influenza and COVID-19 symptoms can be similar, and people will only definitively know which they have with a PCR test.

"Really, without the PCR test you could be suffering from either virus," he said.

"We can detect both influenza and COVID by PCR with a lot of accuracy whereas the RAT tests may be a little bit more hit and miss."

Royal Australian College of General Practitioners ACT/NSW branch manager Associate Professor Charlotte Hespe said rapid antigen tests still return "a number of false negatives".

"PCR still remains what we tend to call a gold standard ... and now we're adding on testing for flu and [respiratory syncytial virus (RSV)], which is the other two big viral causes of very similar illnesses."

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Dr Hespe recommended anyone returning a negative rapid antigen test to immediately get a PCR test, and contact their GP in case they are then able to have an anti-viral medication.

Canberra Health Services chief operating officer Cathie O'Neill said the numbers of patients in Canberra ICUs may be impacted by the flu season.

"We are expecting to see some fluctuations in the number of patients in ICU in the coming weeks, with possible impact from other respiratory infections including the flu," she said.

"Our health services are under more pressure than they have ever been."

The ACT recorded more than 1000 COVID-19 cases for the first time in a month on Wednesday.

There were 1015 new COVID-19 cases recorded in the 24 hours until 8pm Wednesday, and a record high number of Canberrans in hospital with COVID-19 on Tuesday.

Dr Layton said Australia is seeing higher than average flu cases, suggesting it may be peaking earlier than usual.

"For this time of year, we're above the five-year average," he said.

"Typically, it's a little bit later in the year, sort of July onwards, that we start seeing the peak of influenza."

The amount of people with the flu in Canberra remains high and has risen rapidly in children, a report from ACT Health suggests.

ACT Health said while most cases so far have been aged between 20 and 64 years, cases in children aged zero to nine years have increased markedly in the last four weeks.

Cases among people aged between ten and 64 years have declined substantially.

Dr Hespe said people often did not realise how ill children could become from influenza, unlike COVID-19 which did not significantly impact most young people.

"Please do not underestimate the flu. And on top of that, we've had no flu whatsoever in our community for over two years, so everybody's baseline immunity to it has just gone," she said.

"Hence the rising numbers and large numbers of people who've actually needed to go into hospital. And unfortunately, we're not seeing really good vaccination rates, particularly not in the children."

There were 1168 confirmed cases of the influenza reported to ACT Health from January 1 until June 12.

This data does not reflect the real number of flu cases in the ACT, but when compared to previous years it does suggest the flu season has spiked early.

All except one of the positive cases were influenza type A, which is the most common type of flu and has more severe symptoms.

While the current flu has been colloquially called a "super flu", Dr Layton said there was no evidence suggesting symptoms from this strain were worse than in previous years.

"We're not seeing any increase in what would cause severity," he said.

"The difference being that we're just getting a very high number of cases at the moment ... [so] we end up with increased numbers in hospital."

A potential extra burden on the healthcare system is people contracting both the flu and COVID-19 at the same.

Dr Hespe said hospitals were seeing people with both viruses, and GPs had patients who were contracting one virus quickly after the other, and becoming much more sick as a result.

"They haven't actually recovered yet from the first infection and so their lungs are all filled, inflamed and very vulnerable."

Dr Layton said one study suggested contracting both viruses at the same time increased the likelihood of severe illness and death.

He said Canberrans with the flu or any symptoms should act the same as if they have COVID to prevent infecting anyone else.

"Whether you've been tested for it and confirmed positive for influenza or COVID, I definitely would highly recommend minimising your social interactions," he said.

"The type of disease you might have, may not be as severe as someone else."

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However, Dr Layton also said the mortality rate for COVID-19 is higher than the flu.

"The circulating influenza strains don't cause the same level of infections [so] we won't get the same number of cases as we've seen with COVID too," he said.

ACT Health Minister Rachel Stephen-Smith said the influenza had a bigger impact on workforce shortages than COVID-19.

On Wednesday, 85 healthcare staff were off from work across the ACT's public and private hospitals because of COVID-19 but "we've had many more out of the workforce as a result of either themselves having influenza, having other respiratory illnesses or having caring responsibilities for someone who has influenza".

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