Flu cases have shown a slight uptick in the US, primarily due to a small rise in influenza B infections. This is a shift from the more prevalent new K strain that’s been the main focus this flu season.
“We are seeing a second peak, a rebound in flu cases,” noted Dr. Caitlin Rivers, an epidemiologist who shares insights on infectious disease trends. “It’s mainly impacting school-age children,” she explained, particularly those between 5 and 17 years old.
“Kids often lead the way in new trends. So, I believe adults will feel the impact too, but right now, it’s really affecting children,” she added.
Rivers pointed out that this pattern is reminiscent of last year, when flu cases rose again in late February after an initial drop.
She speculated that the recent winter storm, which impacted about half the country, might also contribute to these trends.
Recent data from the US Centers for Disease Control and Prevention shows B strains have increased slightly, under a percentage point, while flu A activity remains steady.
Whether this marks the beginning of a spring wave of influenza B is still uncertain, Rivers said.
Influenza B viruses belong to a different category. Even if someone has had flu this season, they could contract a different strain. The current flu vaccine is designed to protect against two A strains and one B strain, which should help reduce severe illness and hospitalizations.
Both flu A and B tend to share similar symptoms—high fever, sore throat, cough, body aches, and fatigue—and can be treated with antiviral medications.
Overall flu activity remains vigorous, largely driven by the recently identified K subclade of the H3N2 influenza A strain. Typically, years dominated by H3N2 are associated with more severe flu seasons.
In lab test results submitted to the CDC for the week ending January 24, about 87% of cases were attributed to A strains, with roughly 13% to B strains.
The CDC’s national map indicates a considerable flu burden; 29 states report high or very high flu activity, while an additional 10 states show moderate activity.
Eight more flu-related deaths in children were recorded last week, bringing the season’s total to 52.
Among flu, Covid-19, and respiratory syncytial virus (RSV), flu still leads as the dominant respiratory infection, though Covid and RSV cases are on the rise.
