Surging Flu Cases And New Strain Raise Alarms Nationwide

As the United States enters the heart of winter, flu cases are surging to levels not seen since before the COVID-19 pandemic, with health officials and researchers sounding the alarm over a rapidly spreading new strain and a worrying uptick in hospitalizations—especially among children. According to the Centers for Disease Control and Prevention (CDC), as of January 6, 2026, 32 states and jurisdictions are experiencing "high" or "very high" flu activity, a sharp reminder that influenza remains a formidable seasonal threat.

The CDC’s most recent Influenza Surveillance Report, published on December 30, 2025, documented a 6% increase in patients seeking care for respiratory illnesses in just one week. Illinois, for instance, has reported its first child death from the flu this season, and local hospitals are seeing a flood of cases tied to a mutated variant known as Subclade K or "super flu." This new strain, a mutation of influenza A (H3N2), J.2.4.1, has not yet been shown to cause more severe illness compared to previous strains, but its rapid spread and some changes in symptoms have put health authorities on edge.

“Illinois is facing a significant winter surge in seasonal respiratory illnesses with flu activity at very high levels,” Dr. Sameer Vohra, director of the Illinois Department of Public Health, said in a statement. “Vaccinations remain the most effective tool to prevent severe illness from flu, COVID-19 and RSV.”

What’s different about this year’s flu season? For one, the return of classic winter spikes. A retrospective study published in Microorganisms (2025) tracked respiratory infections in Lebanon and found that after COVID-19 non-pharmaceutical interventions (NPIs) like masking and social distancing were lifted in May 2023, viruses such as Influenza A and RSV quickly snapped back to their usual seasonal patterns. Rhinovirus, lacking an available vaccine, remained the most prevalent, but the wintertime clustering of flu and RSV has become the new normal again. “The rollback of containment measures has brought back the winter peaks clinicians used to expect,” the study’s authors noted.

This reversion to pre-pandemic seasonality means that the public and clinicians alike must once again be vigilant for flu symptoms and complications, especially as Subclade K brings some twists. According to Dr. Mark Loafman, chair of Family and Community Medicine at Cook County Health, “More fever with the flu this year than people are accustomed to. And the fever can last up to seven days, so five to seven days. And that's worrisome.” He added that, anecdotally, adults are now experiencing more gastrointestinal symptoms—such as vomiting and diarrhea—than in previous years, a pattern usually seen more in children.

Dr. Juanita Mora, spokesperson for the American Lung Association, described the new strain’s symptoms as “really high fevers. It has a really bad cough that won't go away, very phlegmy, and also vomiting and diarrhea and lots of joint aches as well as muscle aches.” She warned that some fevers aren’t responding to standard treatments like Tylenol or Motrin, underscoring the importance of knowing when to seek medical help.

The CDC lists the most common flu symptoms as fever, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, and fatigue. Vomiting and diarrhea are more common in children, but with the new variant, adults are reporting more gastrointestinal complaints. Not everyone with flu will have a fever, but officials caution that prolonged or unusually high fevers—especially those above 104°F that don’t respond to medication—should prompt urgent medical evaluation.

Other warning signs that require immediate attention include trouble breathing, persistent chest pain, bluish lips or face (particularly in children), severe muscle pain, dehydration, confusion, seizures, and any worsening of chronic conditions. “One is those high fevers that won't break,” Mora said. “Two, the other thing, is any signs of shortness of breath. So when kids or adults are having trouble breathing, they start using their chest muscles, they start wheezing audibly, they start having a cough that won't go away. That's a sign to go to the ER. And the third sign I always teach patients: dehydration.”

Amid these warnings, research is also reshaping how parents and clinicians think about flu treatment—especially in children. For years, the antiviral drug oseltamivir (Tamiflu) was feared to cause seizures and strange behavior in kids. But new evidence, including a large study using Tennessee Medicaid data and following over 690,000 children, has shifted the narrative. The study found that children with influenza who were treated with oseltamivir had about a 50% lower risk of serious neuropsychiatric events, such as seizures and confusion, than untreated children. Children who took oseltamivir without having influenza had rates of these complications similar to those who neither had influenza nor received the drug.

“These findings challenge long-standing warnings about oseltamivir and support its use alongside influenza vaccination to reduce flu complications in children,” reported Medicaldaily.com. The real culprit, it turns out, is the influenza virus itself, which can sometimes cause brain inflammation and severe neurologic symptoms—especially in children with underlying neurologic conditions like epilepsy. For these children, both vaccination and early antiviral treatment are crucial to reducing the risk of prolonged seizures and hospitalizations.

So, how long are people with the flu contagious? According to the CDC and Dr. Loafman, people are most contagious around three days after symptoms begin, but can shed the virus from at least one day before symptoms appear up to seven days afterward. Young children and those with weakened immune systems may be contagious for even longer. Loafman recommends staying home for five to seven days after symptom onset, ideally up to 10 days if possible, and wearing a mask around vulnerable people. “Absolutely great hand washing hygiene so you're not spreading the virus around. And if you can stay in, stay home,” he said.

As for prevention, experts agree: vaccination remains the cornerstone, even if the current flu shot wasn’t specifically formulated for Subclade K. “There has been a lot of talk about the fact that the new variant is not well-covered by it. ... That is true, but you still get protection,” Loafman explained to NBC Chicago. “The vaccine isn't perfect. It doesn't protect all aspects of this from folks. ... But it certainly mitigates the severity of illness.” Those who are vaccinated are less likely to be hospitalized or die from the flu, and it’s not too late to get the shot—protection lasts throughout the season, which can stretch into late March or April.

The combined approach of widespread vaccination, rapid testing, prompt antiviral treatment, and vigilant monitoring for severe symptoms offers the best defense as the nation weathers another challenging flu season. For families, especially those with high-risk children, this layered strategy is more important than ever.

As the flu continues its winter surge, health officials urge everyone to take the threat seriously, get vaccinated if they haven’t already, and stay alert for symptoms—because this season, the stakes are higher, and the virus isn’t pulling any punches.