Health officials report early spike in Influenza A cases in Cook County

Cook County experienced a “tremendous spike” in Influenza A cases in mid-December 2025, according to North Shore Health, prompting local health officials to urge residents to take precautions as flu season continues.

The data comes from a collaboration between North Shore Health, Sawtooth Mountain Clinic and Grand Portage Clinic. The clinics share de-identified patient data to monitor infectious diseases and potential outbreaks, a practice that was implemented following the COVID-19 pandemic.

“When the pandemic ended in 2023, they put the onus of taking care of this information and tracking this for mandates or anything else like that, onto the local health care institutions such as rural hospitals,” North Shore Health Infection Control Director Jason Yuhas told WTIP.

Since then, North Shore Health has tracked influenza trends each season, which typically begins in late September and runs through the end of March.

During the 2024–25 flu season, the largest spike in Influenza A occurred in mid-January. Yuhas said hospital staff expected a similar pattern this year, but the surge came earlier than anticipated.

“The only idea I have is that these virus strains or these bacterial traits will change over time,” Yuhas said. “And based on what we see going from hemisphere to hemisphere, it can have a different time frame. Generally, what we see influenza A again is December into January. January and then influenced the B about the same period of time.”

In response to the early spike, North Shore Health implemented stricter infection-control measures, requiring individuals to either receive an influenza vaccination or wear a mask during the cold and flu season.

As flu season continues, Yuhas encouraged residents to take steps to reduce the spread of illness, particularly during a time when people often travel and spend more time indoors.

“You can have your [family] wear masks, but also, you know, always making sure they wash their hands, making sure they’re staying out of close proximity of individuals that may have known respiratory illnesses as well,” Yuhas said.

Yuhas also emphasized the importance of vaccination. In late December, Cook County reported a fully vaccinated rate of 19.6% among residents.

“Vaccination is an important tool to not only help protect ourselves but more importantly those around us.  At North Shore Health, we care for many elderly and immunocompromised, who could become seriously ill or die from influenza.  Vaccination helps us from spreading influenza to those who depend on us,” North Shore Health CEO, Kimber Wraalstad told WTIP. “It is a very easy and relatively effective way to minimize the spread of influenza.  I believe it is a responsibility we have if we care about those around us.”

WTIP spoke to Jason Yuhas about the data North Shore Health collects to track respiratory illness.  You can find the audio of that conversation below.

Josh Hinke January 6, 2026