Drifted strain
Flu activity in the US remains low for now, but it’s starting to climb. The latest FluView report from the Centers for Disease Control and Prevention shows a steady uptick in test positivity and hospital admissions.
That fits with early warning signs from state data, wastewater readings and Walgreens’ illness tracker, all showing an upward trend. Elsewhere, flu is already surging — a sign of what may lie ahead.
Medical officials in the UK warned this month that a “drifted” H3N2 flu strain is now dominating, with infectioons and hospitalizations both running ahead of schedule. In Japan, outbreaks began a month earlier than usual, forcing widespread school closures, with young children hardest hit.
In China, influenza activity is also climbing. Wang Dayan of the Chinese CDC said last week that H3N2 accounts for more than 95% of all cases. Transmission remains moderate for now, Wang said, but activity is expected to intensify through December. Hong Kong has likewise reported early, sharp increases in flu activity.
Scientists are tracking an H3N2 offshoot known as “subclade K.” It emerged late in the southern hemisphere winter and appears more immune-evasive and less well-matched to this year’s vaccines, which were formulated before it surfaced. Early UK data suggest the shots continue to protect against severe illness.
That may be small comfort for those going into winter under-immunized and under-informed.
CSL, the world’s second-largest flu-shot maker, forecasts a 12% drop in US vaccination this season, including a 14% fall among seniors, based on insurance claims data. Since the Covid pandemic, misinformation about vaccine safety has left roughly 60 million fewer Americans getting annual flu shots — a collapse that helped fuel the most severe US flu season in 15 years last winter.
Experts say the downturn reflects deepening distrust in public health, amplified by politics. Health Secretary Robert F. Kennedy Jr. has upended CDC vaccine units and advisory panels, prompting scholars to warn of “a nightmare” scenario for preventable illness.
Australia’s 2025 flu season, with a record nearing 440,000 confirmed cases, shows what happens when vaccination rates slide and a more pernicious strain emerges.
For the northern hemisphere, the next few weeks will reveal whether it will also learn that lesson. — Jason Gale
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