Chance of early flu season in 2023

Filip Vukasin

23/01/2023 4:49:21 PM

With the pandemic causing unpredictable changes in influenza patterns, the Northern Hemisphere may provide insight on the months ahead.

Child in bed with the flu
Flu cases were much higher in Australia in 2022 than they had been during the first two years of the pandemic.

After a record low Australian influenza season in 2021 and then significantly higher numbers in 2022, experts are preparing for what may come in 2023.
Given Australian influenza epidemics are typically sparked by returned overseas travellers,  reviewing the Northern Hemisphere flu season often provide a glimpse into what Australia can expect later in the year.
Professor Ian Barr, Deputy Director of the World Health Organization (WHO) Collaborating Centre for Reference and Research on Influenza at the Doherty Institute, told newsGP the Northern Hemisphere has experienced an early flu season.
‘It’s similar to what we saw in our flu season in 2022,’ he said.
‘Normally our peak is August, but last year it was in late May and early June then tailed out quickly. The US is seeing something similar.’
According to the Centers for Disease Control and Prevention (CDC), the US hospitalisation rate for influenza at this point in their season is four times higher than any season in the past decade.
Germany has experienced a similar spike, with confirmed influenza cases increasing from 3000 to 56,000 per week over the past month, while in England there was an average of 344 patients per day in hospital with influenza last month – more than 10 times higher than last year’s numbers.
US media had initially labelled their impending winter flu season a ‘tripledemic’ as it began with high rates of COVID, influenza and respiratory syncytial virus (RSV).
However, the CDC states that circulation of these viruses peaked in mid-December, with rates of all three falling in the weeks that have followed since.
Professor Barr says if the Northern Hemisphere has a rebound flu season, cases in Australia might once again spike earlier than usual.
‘We also need to take a view of what’s going on in the region. There is currently an outbreak of influenza in Fiji,’ he said.
‘It’s a numbers game and our coming season depends on the global situation.
‘Last year we saw imports as soon as the law relaxed and the 2022 rates of influenza were high – not record high, but in the top two or three for the past 10 years.
‘There was increased testing through COVID, so that may account for some increase in the numbers.’
Professor Barr says peaks of other viruses have also occurred in Australia recently.
‘There were big metapneumovirus numbers last winter and some of that is still going on,’ he said.
‘It seems to come back every couple of years.’
The WHO announced its recommendation for which strains should be included in the 2023 Southern Hemisphere influenza vaccines last September, providing an impetus for Australia to prepare for our upcoming season.
However, while Professor Barr says having vaccines ready for an early season would be advantageous, he is unsure whether they will be ready in time.
‘Last year, the flu vaccine wasn’t available until April and so only a small proportion of people were vaccinated as there was a rise in cases,’ he said.
‘Hopefully this year it will be available earlier.’
Meanwhile, trials by Novavax continue in Australia and New Zealand for a combined COVID and influenza vaccine. Moderna are also making a combination vaccine.
While neither will be available in 2023, Professor Barr expects COVID and flu vaccination will once again form a major part of Australia’s defences against the viruses.
‘This year, I won’t be surprised if we recommend a fifth dose of COVID vaccine, ideally given at the same time as a flu vaccine,’ he said.
In the meantime, Professor Barr recommends that GPs stay informed about recommendations on influenza vaccination and continue to test for respiratory viruses via multiplex PCR, where possible.
‘I would like to see regular respiratory multiplex tests continue because it will give us a lot of [public health] information,’ he said.
He says expanding testing for respiratory viruses would provide valuable data about trends. The respiratory virus multiplex PCR assay can detect influenza, metapneumovirus, adenovirus, COVID and RSV amongst other infections.
State and territory surveillance reports for influenza are available online, as are the Australian Influenza Vaccine Committee recommendations for the 2023 quadrivalent and trivalent influenza vaccines.
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