Peak Flu Season in Western Colorado: What’s Behind the Surge

While Colorado’s winter snow runs behind schedule, the flu season’s winter surge appears to have arrived early. Flu activity is rising in Colorado and nationwide. This year, the CDC says the dominant H3N2 subclade K strain is to blame.

Reuters reports the strain spreads more easily during winter travel, and in Mesa County, clinics are also reporting a seasonal increase in respiratory illnesses. As the flu season spikes, let's take a closer look at what's going on in Western Colorado.

2025-2026 Flu Season (CDC Trends)

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Reports from the CDC show influenza activity climbing sharply in December, indicating a very active flu season this winter. The CDC's Weekly surveillance reports show illness, hospitalizations, and flu-related deaths all increased from December into January, related to the H3N2 virus subclade K variant. Flu activity maps show this nasty bug is all over the country, with close indoor contact fueling transmission.

Western Colorado & Mesa County: Ground-Level Flu Trends

In Mesa County, local data shows 36 flu-related hospitalizations since October 1, 2025. That’s almost three times the number of hospitalizations at this point last year, with data showing hot spots for the illness centered at schools and nursing homes. While local numbers are at a smaller scale than the CDC’s 81,000 hospitalizations nationwide, the numbers seem to indicate Western Colorado is in the thick of flu season, and now is the time to take precautions.

Why Flu Spread Is Higher This Season (and What You Can Do)

So, what is making this flu season seem so intense? The H3N2 subclade K strain simply spreads like wildfire. One sick person can infect more people in a household or workplace. The holidays create opportunities for exposure, and we all bring them into work after the New Year.

Mesa County Public Health offers the following tips at MesaCounty.US:

• Consider a flu shot: if it is right for you, it may offer some protection.
• Stay home when sick: do not share this gift with others.
• Wash hands often: wash your hands and clean surfaces often.
• Are you coughing or sneezing? Skip crowded indoor settings.
• Severe Symptoms: Contact your health provider early if symptoms are severe.

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