(NEXSTAR) – ‘Tis the season (for respiratory illness).
The latest data from the Centers for Disease Control and Prevention show a rise in people testing positive for influenza and visiting doctors with flu symptoms.
Nationwide, there has been a 5% week-over-week increase in positive flu tests, according to CDC data released Monday. But in a few states, the rise in cases has been even steeper.
For the first time this flu season, two states – Colorado and Louisiana – have broken into the “high” category for flu activity. New York City, which tracks its data separately from New York state, is also showing “moderate” flu activity.
While most states are still seeing “low” or “minimal” flu activity, the recent data still shows cases trending upward. Just three weeks prior, every U.S. state was in the lowest tier, “minimal” category.
The data released by the CDC is on a delay, so it doesn’t yet include the week of Thanksgiving, when many people were expected to travel and gather in large groups.
Public health experts are concerned low vaccination rates will contribute to a bad season like last year’s. Last winter, the flu hospitalization rate was the highest in 15 years.
The uptick in flu activity also comes as a new subvariant of the virus, the K subclade, has emerged. It now makes up a majority of the H3N2 cases we’re seeing. (H3N2 influenza has historically caused more hospitalizations and deaths.)
Cases are expected to continue rising as we get deeper into the typical U.S. flu season. While it varies year to year, flu activity typically picks up in December and peaks between January and March.