Australia's 2026 flu season is late but not over

Australia’s flu season is running late.

Not mild. Late.

Victoria has recorded a 400% increase in influenza notifications over the past seven weeks. Acute respiratory infections in Victorian emergency departments are up 25%. Queensland reported 3,435 laboratory-confirmed influenza cases in recent surveillance data. New South Wales case counts dipped, then rose again through late August and early September. South Australia and Tasmania are tracking rising case counts at moderate levels.

The broader picture: total case numbers nationally remain considerably lower than 2025, which was an exceptionally severe season — over 1,700 deaths, the highest this century. But 2026’s season is running approximately six to eight weeks later than historical patterns. RACGP president Dr Michael Wright has been direct: there may still be another peak ahead, and it is not too late to vaccinate.

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The delayed season pattern

Australia typically sees peak influenza activity in June to August. What is happening in 2026 — a spring surge with active community transmission in September — is clinically and epidemiologically unusual. Data from the Australian Centre for Disease Control and FluTracking Australia confirms the timing shift is real across multiple states, not a local artefact of one jurisdiction’s surveillance.

The practical consequence for patients who made a risk calculation based on the usual season timing is that the exposure window is still open. A patient who declined vaccination in May because the season seemed quiet is now approaching the emerging peak without protection. A patient who was vaccinated early — February or March — may be at the edge of effective antibody response six months later.

Influenza vaccine efficacy wanes over the months following vaccination. The optimal timing for most Australians is April to May. For some individuals vaccinated early in that window, September is now month six of post-vaccination period. The Australian Immunisation Handbook has generally not favoured within-season revaccination — but the waning immunity data is a factor worth considering in the clinical conversation with high-risk patients who vaccinated early and are now asking about their protection.

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Both sides of this

The public health case is clear. Case counts are rising, there is documented emergency department pressure in Victoria, and the RACGP has issued an explicit message urging vaccination. For any unvaccinated patient in a higher-risk group — chronic disease, immunosuppression, aged 65 and over, Indigenous Australians, children under five, pregnant women — the recommendation is straightforward.

The complicating data point: “lower than 2025” does not mean low. 2025 was the worst year on record for influenza mortality in Australia. A season that runs below 2025’s toll but higher than the five-year average, in spring rather than winter, is not a signal to stand down. The timing anomaly also means the usual clinical heuristics — “peak has passed, risk is declining” — do not apply this year.

There is also genuine uncertainty about what comes next. FluTracking and the Australian Centre for Disease Control have the granular weekly surveillance data — their numbers will clarify within the next two to three weeks whether September represents the tail of the season or the beginning of a second wave. Right now, it looks like a season that has not finished.

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What this means in general practice this week

Vaccinate unvaccinated high-risk patients now. The usual reasoning — “the season has peaked, it’s too late” — does not apply in 2026. With active community transmission across multiple states and a possible further peak ahead, vaccination now will still provide meaningful benefit through spring.

Have the conversation with patients who vaccinated early. Those who received their influenza vaccine in February or March — particularly older Australians or those who are immunocompromised — are now six months post-vaccination. Within-season revaccination is not standard guidance, but flagging this for the next autumn vaccination round is appropriate, especially for patients who ask directly about their current protection.

Use point-of-care influenza testing. Victoria’s 25% increase in emergency department presentations for acute respiratory infection is a system-level signal. In general practice, rapid influenza testing is available and helps when the clinical picture fits. Confirming influenza diagnosis shapes management — antivirals prescribed within 48 hours are effective for reducing severity in high-risk patients — and reduces unnecessary antibiotic use at a population level.

Watch the surveillance data. FluTracking’s weekly bulletin and the Australian Centre for Disease Control’s national reporting are the right places to track what happens next. This is a season worth monitoring through October.

2026 has been an unusual season. It has not been a quiet one.

Verdict: yes — the flu season is not over. For unvaccinated patients in higher-risk groups, now is still the right time.

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Sources cited

1. National influenza cases spike later in Australia — ABC News, 18 September 2026
2. FluTracking — National weekly survey of influenza-like illness in Australia