Since Aug. 2025, the United States has been experiencing a rise in a new variant of the flu named “subclade K” or Influenza A (H3N2). This has also been frequently referred to as the “super flu” due to its prevalence and ability to spread rapidly.
According to the Doherty Institute, subclade K was first detected in Australia and New Zealand in Aug. 2025 and began circulating worldwide from there. This strain may be more resistant to immune responses from past infection or vaccination, the institute stated.
The Center for Disease Control (CDC) estimates that there have been between 15 million and 16 million reported cases of the flu since Oct. 2025, with subclade K being the most reported strain. This flu season, there were 40 influenza related intensive care unit admissions in Lake County, a majority of which were patients over age 65, the Lake County Health Department and Community Health Center reported. The county rate of emergency department visits that were flu rated was 4.6 percent for the week of Jan. 4 to Jan. 10, which has dropped from 8 percent for the week of Dec. 28 to Jan. 3.
The WHO stated that every year, approximately 290,000 to 650,000 deaths worldwide are due to flu-related causes. Since this flu season began, the CDC estimates that 3,100 people have died as a result, with children under two, adults over 65, and individuals with chronic conditions most at risk for complications.
Although this variant is largely similar to the flu that circulated in recent seasons, the symptoms are somewhat unique to this strain. Subclade K tends to mutate more often, spreads faster, intensifies common flu symptoms, and can lead to severe respiratory complications, as noted by Nuvance Health. During an interview conducted by NBC Chicago, Dr. Juanita Mora, the national spokesperson for the American Lung Association, emphasized the several key symptoms to look out for when someone does get the flu.
“One, is those high fevers that won’t break,” Mora said. “Two, are any signs of shortness of breath. When kids or adults are having trouble breathing, they start using their chest muscles, they start wheezing audibly, and 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 is dehydration.”
The flu has even reached Stevenson, as some students say they have been affected by the strain. Yana Malpani ‘26 describes her personal experiences with this illness and its symptoms.
“My symptoms included a very high fever, terrible body aches, [extreme] lethargy and fatigue.” Malpani said. “I also had the traditional sore throat, headache, and runny nose. However, I think the most bizarre symptoms were the vomiting and nausea that I experienced which was an unprecedented experience for a common cold.”
Malpani’s journey with the “superflu” brings to life the experiences that Mora depicts in the NBC article. Malpani continues by explaining her doctor’s reasoning behind why the unique symptoms of nausea have been relevant with this illness.
“When I went to the doctor’s office and explained my symptoms, she explained that the more prominent virus this year was influenza A which is more severe than like the common cold or flu.” Malpani said. “She mentioned that despite it being a respiratory tract infection, in children, it causes the inflammation of the GI tract [resulting] in children vomiting when ill with this virus.”
The severity of this new variation is why health officials adamantly encourage immunization as the best safeguard to protect individuals from facing these severe symptoms. Getting vaccinated against the flu is the best way to prevent flu and its health risks for everyone, Mayo Clinic staff said. The vaccine can lower the risk of contracting flu and serious complications.
Doctors encourage these annual immunizations due to their ability to obstruct the potential spread of the virus, especially protecting high-risk individuals from contracting it. The Illinois Department of Public Health (IDPH) indicated that only 24.4 percent of people in Lake County have been vaccinated this flu season, below Illinois’s goal of 70 percent immunization.
A collective action to seek immunization can also mitigate flu spread. Higher immunization rates within a community can contribute to herd immunity, Cleveland Clinic said. Frequent hand washing and sanitizing as well as minimizing contact with sick people are ways to mitigate the spread of flu and avoid contracting the virus along with immunization, the American Red Cross said.
The World Health Organization (WHO) noted that the flu vaccine continues to provide protection against the strain, although its effectiveness is not yet fully understood. Scientists often do not achieve a full understanding of how effective a vaccine is until after the season is over, the WHO explained, because they cannot predict effectiveness for a larger, variable population.
Some individuals avoid the vaccine out of fear of contracting the flu from the shot or believe that the shot is unnecessary if they were previously vaccinated. The American Medical Association (AMA) instead maintained that influenza vaccines cannot cause flu and yearly boosters are essential because immune protection declines over time. Everyone six months and older, the AMA upheld, should get the vaccine.