New data from the Centers for Disease Control and Prevention (CDC) show a sharp increase in flu activity across the United States. This season, there have been at least 7.5 million influenza cases, 81,000 hospitalizations, and 3,100 deaths to date.
Tragically, five new child deaths were reported this week, bringing the season’s total to eight. Public health experts have linked many of these cases to a new flu strain known as subtype K, a branch of the H3N2 influenza A virus.
“Super Flu” K Strain Driving Record Flu Activity Across the U.S.
Experts have referred to subtype K as a “super flu” due to its rapid spread and high infectivity. The strain has been circulating in other countries since summer, driving spikes in Canada, Japan, the U.K., and elsewhere. Among 1,600 flu samples tested by the CDC, about 92% were H3N2, and nearly 90% of these belonged to the K subtype.
Currently, at least 20 states report “very high” respiratory illness activity, including Arkansas, Colorado, Connecticut, Georgia, Idaho, Louisiana, Maryland, Massachusetts, Michigan, Minnesota, Missouri, New Hampshire, New Jersey, New Mexico, New York, North Carolina, Ohio, Rhode Island, South Carolina, and Tennessee. Nine other states, including Alabama, California, Florida, Indiana, Kansas, Maine, Nevada, Texas, and Virginia, report “high” activity.
Flu cases are expected to continue rising in the coming weeks due to holiday gatherings and colder weather. Most outpatient visits for respiratory illnesses involve children and young adults, with 27% of visits nationwide for those under 24, and 15% of patients under five.
In addition to influenza, COVID-19 and RSV are circulating widely, contributing to the overall respiratory illness burden. New York recently recorded the highest number of flu cases ever reported in a single week.
Vaccination Status:
About 130 million flu vaccine doses have been distributed this season, compared to over 143 million at the same time last year. Despite availability, only 42% of adults and children have received the vaccine. The CDC notes that mutations in the new strain reduce vaccine match, but vaccines still help prevent severe illness, hospitalization, and death.
Doctors urge everyone eligible to get vaccinated, emphasizing that it is not too late. Last season, 288 children died from influenza, most unvaccinated—a number comparable to child deaths during the H1N1 pandemic in 2009.
Preventive Measures:
Public health experts recommend frequent handwashing, staying home when sick, avoiding contact with sick individuals, covering coughs and sneezes, and cleaning frequently touched surfaces.
Symptoms and Treatment:
The H3N2 K strain symptoms are similar to typical flu: sore throat, runny nose, fever, cough, headache, muscle aches, fatigue, chills, and sweating. Flu symptoms develop within 2–3 days of exposure, unlike colds, which develop gradually. Vaccines take 10–14 days to build immunity and reduce infection severity.
Experts emphasize that while the K strain spreads rapidly, there is no evidence it is more severe per case than other H3N2 strains. Antiviral medications remain effective, and the flu vaccine provides partial protection against severe disease caused by the K subtype.