Health authorities are issuing a stark warning as an unusual summer surge of influenza grips parts of Australia, driven by a fast-spreading mutant strain of the virus.
Unseasonal Spike in Flu Cases
The Hunter New England region has recorded a significant and concerning rise in laboratory-confirmed flu cases in the final months of the year. More than 630 cases were recorded across October, November, and December. This figure starkly contrasts with the same period last year, which saw 116, 96, and 140 cases respectively.
Professor Nathan Bartlett, a virologist with the Hunter Medical Research Institute and the University of Newcastle, confirmed the unusual trend. "There's a lot of flu around, which is unusual for this time of year," Professor Bartlett said.
The 'Mutant' Strain Behind the Spread
The surge is being primarily fuelled by a specific variant of the H3N2 influenza strain, known as subclade K. This mutant version was first detected in Australia in August and has since been identified in over 30 countries globally.
"It seems to be a bit less susceptible to our immunity, so you get more transmission," Professor Bartlett explained. He added that holiday festivities, where people gather indoors for parties and carol singing, create an ideal environment for the virus to spread rapidly.
The Doherty Institute reports this K variant has been a leading cause of respiratory-related deaths in Australia since its emergence.
National Impact and Holiday Precautions
The Royal Australian College of GPs (RACGP) states that influenza cases have "continued to climb in the summer." Nationally, there have been at least 491,000 flu cases in 2025 so far, representing a 34.5 per cent increase on the record high set in 2024. Alarmingly, flu deaths have surpassed those associated with COVID-19 for the past four months.
In Hunter New England alone, more than 13,000 influenza cases have been recorded this year, the second-highest number on record.
RACGP president Dr Michael Wright urged the public to take precautions during holiday celebrations. "The flu and other respiratory infections can be deadly or put a loved one in hospital," Dr Wright said. He recommended including those who are unwell or isolating in festivities via video or phone calls.
The best defence remains getting a flu vaccination, which experts say still provides meaningful protection despite a noted gap between the vaccine's target and the currently circulating strain. The vaccine is being updated for the 2026 season in response to the virus's evolution.
Disrupted Immunity Post-Pandemic
Professor Bartlett linked the high case numbers to broader changes in population immunity following the COVID-19 pandemic. "Population immunity got completely disrupted over the COVID years," he said. This disruption has increased overall susceptibility, leading to more cases and, unfortunately, more deaths.
The situation underscores the critical role of both vaccination and naturally acquired immunity in controlling the spread of infectious diseases within the community.
