#19,006
It is summer down under, and typically the nadir of the Australian flu season, but this year - as Virologist and blogger Dr. Ian McKay reports - seasonal flu is still going strong more than 3 months after their calendar-based flu season should have ended.
A few days ago Ian wrote:
Instead of the annual epidemic returning to baseline levels, cases stopped declining in October and have started to rise again in November, December, and perhaps also in January (still a few days left). Just to note, there is always some flu around, just usually at very low levels outside the epidemic peak period.
I would invite you to read Ian's entire analysis, because the same subclade K of seasonal H3N2 which emerged there last July, is now running roughshod over the United States, Canada, Europe, Asia, and the rest of the Northern Hemisphere.
Due to the holidays, surveillance and reporting over the past few weeks have likely under-represented its current impact here in the United States. We'll get another belated FluView on Monday, but it often takes until mid-January before reporting returns to normal.
Meanwhile, early reports (see WHO EURO Statement: More than half of WHO European Region experiencing intense, early influenza season driven by new strain) and the latest FluView data (which is at least 2 weeks old at this point), attest to its impact.
Whether we'll experience the same protracted flu season as has Australia remains to be seen - but it is certainly possible - making it still very much worth getting this year's flu vaccine if you haven't already.
Despite concerns that this year's vaccine may not be as effective against this drifted subclade; it is still expected to provide valuable protection against severe disease (see UKHSA Preprint: Early Influenza Virus Characterisation and Vaccine Effectiveness in England in Autumn 2025, A Period Dominated by Influenza A(H3N2) Subclade K)
How much protection? Well, we probably won't have good data until later this month, and the full story won't be known until next summer. But anything that reduces your chances of being hospitalized with severe influenza has value.
Which is why I also wear a mask in public, use copious amounts of hand sanitizer, and try to avoid crowded indoor spaces. A strategy which has helped keep me respiratory illness free for nearly 5 years.
Last year was pegged as being the worst flu season in nearly a decade (see MMWR: Influenza-Associated Hospitalizations During a High Severity Season (United States, 2024–25)), but this year could end up being even more challenging.
Already New York state is reporting a faster start to this year's flu season (see dashboard below) and last week their DOH reported (New York State Department of Health Confirms Most Flu Cases Ever Recorded in One Week).
While many people trivialize the flu, numerous studies suggest strong links between influenza infection and cardiovascular events like heart attacks and strokes (see also Eur. Resp.J.: Influenza & Pneumonia Infections Increase Risk Of Heart Attack and Stroke).
In early 2023, in Neuron: Virus Exposure and Neurodegenerative Disease Risk Across National Biobanks, we also looked at a study published in Cell Neuron which found a statistical linkage between viral illnesses and developing neurodegenerative diseases later in life.
- In 2008, H1N1 abruptly developed nearly 100% resistance to oseltamivir;
- In 2014, we saw a late summer mutation appear in the H3N2 virus (see HAN Advisory On `Drifted’ H3N2 Seasonal Flu Virus) which greatly reduced the effectiveness of that year's flu vaccine.
- in 2016, we saw warnings over mutated (D225G) H1N1 viruses in Russia and in Europe (see ECDC Risk Assessment : Reports Of Severe A(H1N1)pdm09 In Europe);
- And while it has had only limited impact so far, we are now watching another slow rise in antiviral resistance in H1N1
This graphic comes from the March 16th, 1951 Proceedings of The Royal Society of Medicine – page 19 – and shows in detail the tremendous spike in influenza deaths in early 1951 over the (admittedly, unusually mild) 1948 flu season.
In 2006 the CDC's EID Journal published a stellar account of this event, and it is very much worth reading.
Viboud C, Tam T, Fleming D, Miller MA, Simonsen L. 1951 influenza epidemic, England and Wales, Canada, and the United States. Emerg Infect Dis [serial on the Internet]. 2006 Apr [date cited].
