Flu season has hit early and hard in the East, with New York experiencing a record number of cases of the viral respiratory illness. The state’s health department reported that 71,123 influenza cases were confirmed for the week ending Dec. 20 — the most ever recorded for a single week.
Because of the holidays, the Centers for Disease Control and Prevention report is behind a week. But as of Dec. 13, CDC reported at least 4.6 million cases of flu nationwide, with 49,000 hospitalizations and 1,900 deaths.
Multiple states have reported high or very high number of visits to doctors and clinics for influenza-like illnesses. The illness is trending upward in nearly every state, with symptoms that include fever, coughing, headaches, muscle aches and exhaustion.
While the trend nationally is expected, there’s concern that a new strain of flu called subclade K, which is not a great match for the current vaccine, may increase cases. But health officials say that the flu vaccine should prevent serious illness even in those with the A(H3N2) variation. The H3N2 influenza family is said to cause harsher flu seasons.
As Newsweek reported, “Subclade K has developed small genetic changes that set it apart from the H3N2 strain used to make the 2025 to 2026 U.S. flu vaccine. This kind of change, known as antigenic drift, is common for flu viruses and happens as they evolve over time.”
CDC noted that 89% of H3N2 flu samples have been subclade K since September.
During a video briefing Dec. 16, the co-director of Johns Hopkins University’s Center of Excellence for influenza studies and response Andrew Pekosz called it “clear” that the number of flu infections are increasing nationwide.
At the same time, the number of people receiving flu shots has been falling. CDC reported that more than 47.6 million flu vaccines were given to U.S. adults so far, but that’s about 3 million fewer than this time last flu season. CDC recommends that everyone 6 months and older be vaccinated against the flu.
Enough viruses to go around
There are other viruses circulating right now, as well: The common cold, influenza strains, COVID-19 and respiratory syncytial virus (RSV) are all making the rounds. And it’s sometimes hard to tell the difference without a lab test.
One way to tell flu is by its sudden onset and symptom severity. One minute you’re okay and the next you feel awful. Quick onset typically indicates flu.
According to that most recent CDC report, the states hardest hit by flu are New York, Rhode Island, Colorado and Louisiana. Flu activity is high in Connecticut, Georgia, Idaho, Maryland, Massachusetts, Michigan, Minnesota, New Mexico, North Carolina, Ohio and South Carolina. But the data is two weeks old and other states are believed to have very high flu activity, as well. In South Carolina, Prisma Health announced that as of Dec. 26, no one age 15 and younger will be able to visit patients in its hospitals because of the increased incidence of flu, per The State.
Utah was listed as a state where flu activity was moderate. The Utah Department of Health and Human Services is reporting 391 people have been hospitalized with flu so far this season.
Is it too late for a vaccine?
It’s not too late to be vaccinated, health officials have told Deseret News. Pamela Gomez, respiratory disease epidemiologist in the Utah Department of Health and Human Services, said recently that people should still be vaccinated against the flu. “As soon as possible is the best action,” as even a less-than-perfect match will help keep those who get the flu from hospitalization. It should still reduce the severity should one be sickened by influenza.
Per the Deseret News article, “While the vaccine’s makeup does not directly include subclade K, it does provide related influenza A protection, which should buffer some against subclade K’s severity were someone to become infected. And subclade K will not be the only flu variant to which people are apt to be exposed this winter.”
While flu is already circulating, it typically peaks in February, so vaccination is likely to prevent illness or make it milder for lots of people.
The Hill quoted Pekosz: “It’s very difficult to predict a flu season, but right now, we’re at the beginning of what we probably are going to see as a pretty severe influenza season. We think this subclade K virus is evading population immunity, meaning more people are susceptible to infection because it has mutations that are making it less able to be recognized by your body’s immune system.”
People are so used to flu that they often forget that the virus can pose very serious complications and even kill. Those most vulnerable are children under 5, older adults, pregnant women, those with chronic conditions, people with weak immune systems, residents of long-term care facilities and people with disabilities, per CDC.