Australia has recorded its largest number of laboratory-confirmed influenza virus detections among sick people for any July on record. While the numbers may be slowing, there is no way of knowing how long the peak will last or whether we’re in for a quick decline or a prolonged, painfully slow decline.

Number of people testing positive for influenza (“detections”)

As always, it’s the 𝙩𝙧𝙚𝙣𝙙𝙨 we’re looking at because there’s no way that every actual infection can be captured, so the data we have may not be the data we want, but they’re the data we’ve got.

Another 23,233 detections were added to the Australian National Notifiable Disease Surveillance System (NNDSS) over the past eight days.

As you can see from the graph below (follow the red dashed line with circle markers, for 2025), the core part of the 2025 winter flu season has closely mirrored the numbers seen in 2019 (pale green line, triangle markers), the last year before the pandemic began.

There was one noticeable difference from any other year on record, though, and that’s the much higher load of detection cases in the first three months of the year, which is typically the inter-epidemic trough.

It also appears that July may be seeing a slowdown in cases; the line rises less steeply than it did between May and June, although there are still a few days of July left. And it’s worth remembering that a peak is only the highest point of detections; we still have to come down the other side of the mountain. We don’t know how long we’ll be at the peak, nor how sharp or flat the slope downwards will be. We could still have a lot of flu circulating among us for weeks to come.

Flu by month and jurisdiction within Australia

Next, we break down the monthly totals by each Australian jurisdiction – six states & two territories for my overseas readers.

Boxes grouped by x-axis scale. As with any large area of land, the spread of viruses is influenced to some extent by the societal and environmental factors of the region.

Winter education holidays are over, so we may expect the peak to last a little longer yet. Allow for the incubation time from children returning to school, mixing, becoming infected, and spreading the virus among their households and public transport, etc. Same as every year.

It appears that Victoria, the ACT, and Tasmania have slowed the most, while NSW, Queensland, and the Northern Territory are rising fastest, based on these data.

Year-on-year comparison

The comparative annual totals show that 2025’s total lab-confirmed virus detections (=”notifications”) are closing in on the top-five-biggest-years territory.

I also show when different PCR testing (we refer to these as “molecular tests”) was implemented. PCR is a more sensitive and faster method, and more of it came online after the 2017 #Flunami season (now not as headline-worthy compared to subsequent years).

In particular, during the pandemic, numerous rapid PCR-based point-of-care tests (POCTs) were introduced into laboratories. These, while more expensive than higher-throughput real-time PCR-based methods, increased the ease with which a flu test could be conducted and the speed with which results could be obtained (under two hours), making a huge difference when managing bed use in a hospital setting. You’ve heard of ‘ramping’, right?

The reason I add those details is to highlight that we have changed testing in several ways, and that can also have an impact on how many tests are ordered by Doctors.

Influenza detection by age group

This is pretty standard stuff. Influenza virus is detected most commonly among young people, especially those under 10 years old. The young transmit it effectively amongst themselves at their daily mass gatherings (education). Then to their parents (the next bump in the graph).

The elderly are most affected by influenza-they bear the biggest burden of disease, followed by the young. We’ll look at clinical impact in the next section.

Clinical severity of 2025 so far

To understand the clinical severity of the season, we can refer to a definition that the brilliant crew has already established at the Australian Government’s Department of Health and the ACDC, who also prepare the fortnightly Australian Respiratory Surveillance Report (ARSR) from which the next graphs come.

The image below comes from the ARSR Technical Supplement. It tells us that we need to consider multiple sources of illness to understand how ill we are, not just the number of infections, which alone indicates good testing and a high number of infections, but doesn’t tell us how ill the people providing the samples are.

Illness indicators include:

• Absenteeism
• GP networks
• Hospital & ICU admissions
• Deaths

The data used to create the graphs above is from the NNDSS and is more up-to-date, but it doesn’t provide any clinical details. The latest fortnightly report has data up to July 13th. A fair while back in the past, so it’s hard for the community to use this report usefully in judging the risk of harm right now from influenza. But it is what we have in lieu of a real-time dashboard setup like other countries seem capable of.

According to it…

Absenteeism

Fewer people reported taking time off compared to the week before.

GP Networks

A slight rise in influenza-like-illness (ILI) symptoms of new fever and cough.

Hospital and ICU admissions

A selected panel of sentinel hospitals shows an increasing trend in admissions for severe acute respiratory infections since late March (about Week 12 onwards). Flu has dominated in the most recent weeks with a 53% increase in the past fortnight (up to June 29th).

Most of the admissions in 2025 were due to influenza A (82%). Of those that were subtyped (20%), most were A(H1N1) (93% of the influenza As) and the rest A(H3N2).

An increasing trend since May is for intensive care unit (ICU) admissions with influenza (only up to June 29th). Most admitted to an ICU were infected with a rhinovirus/enterovirus, followed by influenza virus, which is more likely to require mechanical ventilation.

Deaths

Death data are a bigger lagging indicator – it takes more time to collect these numbers – but what’s clear from the data up to May is that COVID-19 is the primary respiratory virus killer (I hope you’re all up to date with that vaccine), but influenza is next in line, killing every month. In somewhat good news, COVID-19’s murderous rampage is decreasing year-on-year.

Vaccine match and uptake

According to lab tests, the vaccine is a good match for the circulating influenza variants. However, more useful vaccine effectiveness studies of human outcomes aren’t released until after the peak of the season.

Vaccine uptake is pretty poor among all age groups, but particularly among the young who are being hit hard by flu this year. Vaccine misinformation, America and social media non-expert idiot motor-mouth are undoubtedly playing a big part in making those who are already vaccine-hesitant put off getting their children vaccinated. Additionally, there’s insufficient effective and authentic local communication about the importance of this safe vaccine, and perhaps not enough proactive reminders by GPs and educational facilities for parents to get their children vaccinated. Maybe we can all do more to promote vaccination next year?

Which influenza viruses are dominating?

The influenza A(H1N1) subtype is dominating overall this season. It appears that it was its turn in the battle for influenza A domination.

The next graph – while a little difficult to discern at times – shows the influenza Bs (pale blue) and the three groups of influenza A – unsubytped (dark blue), subtype A(H1N1) (red) and subtype A(H3N2) (pink) across four key age demographics. Subtype A predominates among babies and the very young, whereas influenza B has a more significant impact on the 5-16 year old age group. Among adults, influenza A is locked in – for some reason I don’t understand, the greater extent of influenza A subtyping in adults allows us to clearly see A(H1N1)’s dominance.

Summary

It’s been a huge influenza season in terms of laboratory detections, and clinically, the lagging national report shows data that support a rising clinical burden as well. This has also been described in various media stories. Still, it’s hard to gauge, given it’s rare to see in these stories of a “terrible year” and “big rise in hospitalisations” any comparison to past years to understand if things are truly different from what we experience every season or if human recall bias is playing a part. Nonetheless, it’s clear that Australia is amid its predictable annual epidemic of circulating influenza infections, and these are causing disproportionate harm in a population that is poorly vaccinated.

However, as of July 13th, there has not been an equally exceptional level of severity.

The main virus circulating is A(H1N1), but as usual, all flu subtypes/lineages are co-circulating and having an impact. The Rhinoviruses are also having a big clinical impact within adults and especially in children with SARS-CoV-2, RSV and the parainfluenza viruses, next in line to cause us anything from mild illness to severe disease and misery in 2025.

There are tools and interventions you can use to reduce your infection risk, such as a vaccine, mask, and social distancing. Please think carefully about using all of them. As usual, we still await the appearance of new influenza vaccines that offer fewer regular shots and are more effective – the magical “universal flu vaccine”.

But for now, it’s not too late for you or your friends to book online and drop into a chemist to get a shot. My whole family got ours this way. Dad can even organise it! It really doesn’t take long, and there is still a lot of wind left in this flu season’s sails. And while you’re at it, consider setting a reminder on your phone for March 2026 to stay alert for the next vaccination campaign season.

Let’s prevent…