Infectious disease experts have issued a fresh warning to West Australians planning trips to the northern hemisphere, urging them to consider getting an influenza vaccination. This advice comes as Western Australia experiences an unusual late-season spike in a severe strain of the flu, predominantly affecting older adults.
An Unusual Late-Season Flu Trend
After influenza notifications had been steadily declining from a peak of 1704 weekly cases on September 7, recent WA Health data reveals a concerning new trend. Cases rose to 661 in the week leading up to November 2.
This increase is largely driven by a late surge in the influenza A H3N2 subtype. For most of the year, the A H1N1 subtype was responsible for the vast majority of WA's flu cases. However, the proportion of A H3 detections has dramatically shifted from just 2 per cent in mid-July to 70 per cent by November 2.
Professor Asha Bowen, a clinician and researcher at Perth Children’s Hospital and The Kids Research Institute, confirmed the unusual nature of this trend. "Every year we have these two competing types of influenza A, and usually we see the same virus throughout the season," Professor Bowen said. "This is a slightly different trend."
Global Concerns and Travel Advice
The local situation is unfolding alongside warnings of an early and potentially severe flu season in the northern hemisphere. Of particular concern are mutations of the A H3N2 virus detected in the UK, which are reported to be evading immunity.
Professor Bowen emphasised the importance of vaccination for travellers. "Plenty of people head over to the northern hemisphere for the winter season so we are continually encouraging people travelling to think about getting the flu vaccine," she stated.
Professor Jaya Dantas from Curtin University noted that it is unclear if these specific mutations have reached Australia. She suggested that international travel and WA's cool, wet spring could be contributing to the rise in local cases, but assured that the overall trend is mostly downward and not a major cause for concern.
Call for Enhanced Vaccination Campaign
This year, WA has recorded a staggering 32,560 flu cases, a figure well above the five-year average of 13,935. Hospitalisations are also almost double the average, sitting at 4532 patients.
Despite this record-breaking season, only one in four people in WA is vaccinated against influenza. Professor Dantas has called for an accurate and sustained public awareness campaign to boost these rates, particularly ahead of next winter. "The vaccine does prevent the severity, but we need to increase vaccination rates with evidence-based information, especially from March onwards," she said.
A WA Health spokeswoman confirmed that influenza levels remain well above typical levels for this time of year, largely due to the A H3 strain. She noted that this subtype commonly impacts the elderly, with around two-thirds of cases occurring in adults, and that international travel is a known contributor to the spread of such viruses.
