Sixteen children died of the flu in the week ended January 27, bringing total pediatric deaths to 53 for the season, according to the Centers for Disease Control and Prevention's weekly report.
Out of every 100,000 people in the general population, an estimated 51.4 have been hospitalised for the flu, surpassing the rate in the last severe season of 2014-2015, when 710,000 were hospitalised and 148 children died. Adults aged 65 or older had the most hospitalisations, followed by those aged 50 to 64 and children below 5.
"So far this year the cumulative rate of hospitalisation is the highest since we began tracking in this way," Dr. Anne Schuchat, acting director of the Centers for Disease Control and Prevention, told reporters on a conference call.
With the previous record now broken, "we fear this year might be even worse than 2014-2015," Schuchat said in a telephone interview.
The United States is now 10 weeks into the current flu season, which is expected to last for at least several more weeks.
The dominant strain during this flu season is an especially nasty type called influenza A (H3N2) that in seasons past was linked with severe disease and death, especially in the elderly and young.
Schuchat was named acting CDC director earlier this week after Dr. Brenda Fitzgerald resigned from the post because of financial conflicts of interest, including purchases of tobacco and healthcare stocks while in office.
Flu is widespread in 48 states, down from 49 last week, with Oregon reporting less flu activity, the CDC said.
"We are not out of the woods yet," Schuchat said, noting that sick people should stay home to avoid transmitting the virus to others, frequently wash hands and cover their mouth while coughing or sneezing.
The CDC official also said it was not too late to get a flu vaccine.
(Reporting by Deena Beasley; Editing by Richard Chang and Cynthia Osterman)