Chicago and the U.S. rang in the new year with a flurry of flu cases, setting 2025-26 on pace to be one of the busiest influenza seasons in years.
Flu seasons can vary year to year, but the season usually is most intense from December through February, and cases can continue into the spring.
Flu is in the spotlight this season, with not only more cases compared to other years at mid-season, but also a record number of emergency room and clinic visits, according to the CDC.
A new variant of influenza, called “subclade K,” evolved from prior variants of the H3N2 influenza virus, and its mutations have enhanced its ability to transmit more easily by evading people’s immunity.
Take flu seriously
Vaccines remain one of the most effective tools for preventing serious illness, protecting people who are at greater risk of illness and reducing the spread of disease. While the vaccine may not always prevent infection, it can prevent more severe illness, said Michael Lin, MD, Rush infectious diseases specialist.
“Flu is familiar, so people forget how dangerous it can be. The vaccine’s most important job is to keep you from getting seriously ill,” Lin said.
Other measures add another layer of protection. “What protects you from flu — masking and hand hygiene —helps guard against other respiratory viruses,” he added.
Flu vaccines are updated annually and are recommended every year for anyone over the age of 6 months. Flu vaccines are being offered by many pharmacies, doctors’ offices and public health departments, and it’s not too late to get a vaccine.
Who should see a doctor?
Flu antiviral treatment is recommended for older adults, young children, pregnant people and anyone with chronic medical conditions. These medications help prevent the flu from turning into a pneumonia or requiring hospital care.
If you are having trouble breathing, chest pain, confusion, dehydration or worsening symptoms, see a doctor right away.
If you’re older, pregnant, or have chronic medical conditions, contact a provider within a day or two – because you may qualify for early antiviral treatment.
Everyone else with mild symptoms can recover safely at home.
