Australia Records Highest Influenza Death Toll This Century in 2025

Influenza deaths in Australia exceeded COVID-19 mortality for the first time since 2020, driven by a new viral variant and declining vaccination rates.

The Australian Bureau of Statistics (ABS) and the National Notifiable Disease Surveillance System (NNDSS) have confirmed that 2025 saw approximately 1,701 influenza-related deaths—surpassing the previous record of 1,656 set in 2017. COVID-19 deaths totaled roughly 2,161 in 2025, a significant decline from 5,108 in 2024. RSV-associated deaths numbered approximately 582.

Nearly 500,000 laboratory-confirmed influenza cases were recorded in 2025, the highest since records began in 1991, with Queensland alone reporting 93,764 cases. Over 500,000 cases were also captured through laboratory surveillance systems.

The Circulating Variant: Subclade K ("Super-K")

A new variant of Influenza A(H3N2), designated subclade K and colloquially known as "Super-K," has been identified as a key driver of elevated transmission. Genetic analysis reveals mutations in the hemagglutinin protein that differ from strains used in existing vaccines, potentially reducing protection from prior immunity or vaccination.

First detected in the United States in mid-2025, researchers at the Peter Doherty Institute identified it in Australia by September 2025. By October, it had become the dominant circulating strain nationally.

"Subclade K is not inherently more severe than other H3N2 strains, but its higher transmissibility leads to more infections, resulting in more severe outcomes overall."

The variant has been detected in over 30 countries, including the United States, United Kingdom, Japan, Canada, and Indonesia. The UK Health Security Agency reported that 87% of H3N2 viruses detected since late August 2025 were subclade K.

Seasonal Patterns and Timing

The influenza season in 2025 displayed unusual persistence into spring and summer, defying typical seasonal patterns.

Between January and July 2025, COVID-19 deaths (1,279) exceeded influenza deaths (682). However, between August and December 2025, influenza deaths reached approximately 741, overtaking COVID-19 deaths (428) .

By mid-November 2025, weekly emergency department presentations for influenza-like illness in New South Wales exceeded 370. In late December, the NSW Respiratory Surveillance Report recorded over 3,000 laboratory-confirmed notifications weekly—a 15% week-on-week increase during a period when influenza activity typically declines.

For 2026, influenza activity was described as "currently low and relatively stable" by the Australian Centre for Disease Control as of late February. However, health authorities anticipate increased transmission heading into winter. Most cases are among children under nine and adults over 75.

Declining Vaccination Rates

Vaccination rates have dropped across all age groups since 2022:

Health authorities attribute declining rates to pandemic fatigue and misinformation regarding vaccines.

Vaccine Composition and Effectiveness

The 2026 influenza vaccine for Australia has been updated to include strains closely related to circulating subclade K viruses:

• An A/Missouri/11/2025 (H1N1)pdm09-like virus
• An A/Singapore/GP20238/2024 (H3N2)-like virus
• A B/Austria/1359417/2021 (B/Victoria lineage)-like virus

Preliminary data on vaccine effectiveness:

• Australian data (2025): Vaccinated individuals were 53% less likely to be hospitalized or visit a GP for flu symptoms
• UK data (2025-26 winter): 72–75% effectiveness in protecting children and adolescents against medically attended flu cases, including subclade K
• EU research: 72.8% effective in preventing hospitalization in children; 66.3% for adults 18–64; 31.7% for those over 65

The CDC estimates that 130 million doses of influenza vaccine have been distributed in the United States.

Vaccination Recommendations

Annual influenza vaccination is recommended for individuals aged six months and older by the Australian Department of Health, the CDC, and major medical organizations.

"Vaccination, even if it does not prevent infection, reduces disease severity and hospitalization risk."

The flu vaccine is available free under the National Immunisation Program (NIP) for eligible groups:

• Individuals aged 65 and over
• Children aged 6 months to 5 years
• Pregnant women
• Individuals with chronic health conditions

For those not covered by the NIP, the standard vaccine costs between $20–$38. A higher-dose vaccine for older adults is priced around $75.

The recommended period for vaccination is April to May, allowing approximately two weeks for immunity to develop before peak season. Protection typically lasts three to four months at optimal levels.

Treatment

Antiviral medications, including oseltamivir (Tamiflu), can reduce symptom severity and illness duration when administered within one to two days of symptom onset. The CDC recommends prompt antiviral treatment for individuals at higher risk of severe complications, including pregnant individuals and those with chronic conditions.

Far North Queensland Regional Situation

Far North Queensland recorded more than 300 laboratory-confirmed influenza cases from January through early 2026, exceeding typical counts for the period.

The region is experiencing increased international tourism, particularly from Indonesia, following the restoration of direct air routes between Bali and Cairns in August 2024 by AirAsia Indonesia.

Regional factors compounding the situation:

• Recent heavy rainfall and flooding have strained hospital capacity and disrupted primary care access in remote communities
• Influenza circulates year-round in tropical regions, including Far North Queensland and Southeast Asia
• Queensland's surveillance systems indicate influenza activity is exceeding historical seasonal norms

No universal symptom screening for influenza is currently conducted at Cairns Airport for arriving passengers. The Cairns Public Health Unit conducts surveillance monitoring of arrivals from regions with high influenza activity.

International Context

United States

The CDC reported high or very high influenza activity in over half of U.S. states as of late December 2025. By mid-January 2026, the CDC estimated at least 15 million influenza illnesses, 180,000 hospitalizations, and 7,400 deaths, including 17 pediatric deaths. Over 91% of A(H3N2) virus samples collected since late September 2025 were subclade K.

The CDC described the current season as among the highest in cases observed in nearly 30 years.

United Kingdom

The 2025-26 influenza season began earlier than any season since 2003-04, according to health authorities.

Japan

The influenza epidemic began in late September 2025, earlier than the typical December–February peak. The Ministry of Health reported that 22 of 23 H3 virus strains collected between September and November were subclade K.

California

The California Department of Public Health reported elevated seasonal flu activity, with a rise in flu test positivity rates beginning in mid-December. Los Angeles County recorded 162 flu-related hospitalizations and 18 intensive care admissions between late 2025 and early 2026.