The flu season is upon us, and it's bringing some unexpected twists this year! The World Health Organization (WHO) has released a report, and the news is that influenza A viruses are currently dominating the global flu scene. Let's break down what this means and why it matters.
Since October, the activity of influenza has been on the rise worldwide. This increase aligns with the onset of winter in the Northern Hemisphere, where we typically see a seasonal surge in acute respiratory infections. These infections are caused by a mix of culprits, including influenza, respiratory syncytial virus (RSV), and other common respiratory viruses.
While the overall influenza levels are within the expected seasonal range, some regions are experiencing an earlier and more intense activity than usual. Specifically, influenza A (H3N2) viruses are playing a significant role. But here's where it gets controversial...
Predicting the exact timing, duration, and severity of each flu season is tricky. It all depends on the types of viruses circulating, how well the population is protected (immunity), and even the weather conditions. Some Northern Hemisphere countries are seeing an early start to the flu season, although it hasn't yet reached epidemic levels. Meanwhile, some parts of the Southern Hemisphere have already experienced above-average virus activity in recent months.
Across various regions – temperate, sub-tropical, and tropical – there's been an increase in the detection of H3N2 viruses. Since late September, this has become the dominant strain.
It's also worth noting that seasonal influenza viruses are constantly evolving. Since August 2025, there's been a rise in the detection of H3N2 J.2.4.1 (also known as K subclade) viruses in several countries. These K viruses have shown some genetic changes compared to related H3N2 viruses. And this is the part most people miss...
Although these genetic changes exist, current data doesn't suggest an increase in the severity of the illness.
The WHO emphasizes that vaccines remain crucial, especially for those at high risk of flu complications and their caregivers. Even when the circulating strains differ slightly from those in the vaccines, the seasonal flu vaccines can still provide protection.
What are your thoughts on this year's flu season? Do you think the vaccines are effective? Share your opinions in the comments below!
