The flu season is picking up pace, new data from the Centers for Disease Control and Prevention shows. And it’s looking to be a doozy this winter.
According to the CDC’s surveillance, seasonal flu activity has increased throughout most of the country in recent weeks. Surges of flu have already led to school closures in some areas, while at least one pediatric death has been recorded so far. This season is being driven by a novel variant of H3N2 flu, dubbed subclade K—a variant that our vaccines are ill-equipped against.
An emerging, unexpected threat
During a flu season, multiple variants of influenza A and influenza B viruses will spread between people. Because conventional vaccines take time to produce, public health experts try to predict which flu strains will be circulating up to nine months before flu season starts in each hemisphere.
This winter, however, subclade K has thrown a wrench into our plans. The variant emerged toward the end of the winter in the Southern Hemisphere, and it’s proven to be genetically different and fit enough to quickly supplant other strains of H3N2 and other flu viruses in general. What’s worse, the seasonal flu vaccine is poorly matched to subclade K, reducing its ability to prevent infection and illness from the strain.
The emergence of subclade K already extended the flu season in parts of the Southern Hemisphere like Australia and New Zealand. It’s also jumpstarted the flu season weeks ahead of schedule in European countries. In the UK, subclade K is currently helping cause a spike of hospitalizations and an “unprecedented wave of super flu,” according to NHS officials.
The CDC’s latest data, covering the first week of December, shows that respiratory virus activity in the U.S. is low overall, but this peace likely won’t last long. Flu cases meriting medical care are rising in most parts of the country, with 8.1% of lab tests coming back positive for flu (two weeks earlier, it was 5%). Flu-related hospitalizations also appear to be increasing, and the first pediatric death linked to flu was reported last week. And schools in Missouri and Iowa have already had closures due to recent flu outbreaks.
What to do about the flu
The majority of new infections in the U.S. are being caused by H3N2, signaling that subclade K is rearing its ugly head here, too. And given what’s happening in other parts of the world, that doesn’t bode well for us.
That said, vaccination does remain an important part of staying safer this flu season. Despite the mismatch to subclade K, early UK data has found that the seasonal vaccine is still effective at preventing severe illness from the flu, particularly in kids.
You should also practice good hygiene like regularly washing your hands, try to stay home if you’re sick, and potentially wear a mask in higher-risk situations for added protection (well-fitting, high-quality masks such as a KN95 or N95 being the most effective).