Influenza cases are rising sharply, with an estimated 7.5 million people sickened, 81,000 hospitalized, and 3,100 deaths.
Influenza cases are rising sharply, heightening fears that a new strain will fuel a punishing flu season that is already outpacing last year's.
The flu has sickened an estimated 7.5 million people so far this season, according to weekly data from the Centers for Disease Control and Prevention released Tuesday. About 81,000 people have been hospitalized and 3,100 have died so far this flu season, the agency estimated, including eight children. That reflects a sharp increase from the week prior, in which the CDC estimated about 4.6 million cases, 49,000 hospitalizations and 1,900 deaths.
Roughly 25% of samples sent to clinical laboratories came back positive for the flu in the week ended Dec. 20, the CDC said. That is up from about 15% the week before.
The figures raised concerns of a particularly harsh flu season this winter. The contagious respiratory illness typically kills thousands of people in the U.S. each year, though that number can rise significantly in years with troublesome viral variants.
Of particular concern this year is a variant of the H3N2 virus known as subclade K. H3N2 has dominated the U.S. flu season thus far -- and roughly 90% of the H3N2 samples the CDC characterized since late September are subclade K, the agency said.
The 2025 flu shots protect against H3N2 and two other flu viruses. Public-health officials say it provides some protection against subclade K, though it wasn't designed to target the strain in particular. Officials say it's not yet clear if subclade K is more likely to cause severe illness.
While it's still early in the flu season, which typically peaks between December and February, the 2025 figures are significantly outpacing last year's tally. At this time in 2024, the agency estimated approximately 3.1 million illnesses, 37,000 hospitalizations and 1,500 deaths.
Residents of New York, South Carolina, New Jersey, Colorado and Louisiana have been especially hard hit this season, according to CDC data on respiratory illnesses. That data measures illnesses that include a fever and a cough or sore throat, which should capture the flu but may also include other pathogens.
New York state said it recorded its highest-ever tally of flu cases -- 71,123 -- for the week ended Dec. 20, a 38% jump from the week before. Hospitalizations jumped 63%, the state's health department said.
The CDC recommends that everyone 6 months and older receive a flu vaccine. The agency said roughly 130 million doses of the vaccine have been distributed thus far this season.