Flu is surging nationwide. Hospitalizations nearly doubled in a single week.

Flu is surging across the U.S., sending thousands more people to the hospital and hitting young children especially hard, as doctors warn the season still has a long way to go

Flu is surging across the U.S., sending thousands more people to the hospital and hitting young children especially hard, as doctors warn the season still has a long way to go.

Flu activity is at “high” or “very high” levels in 32 states and jurisdictions, based on data from the week ending Dec. 20, the Centers for Disease Control and Prevention reported Tuesday — up from 17 the week before. At least 7.5 million have gotten sick since the season began in October.

Hospitalizations nearly doubled in a single week, rising to 19,053, up from 9,944 the week prior, according to the CDC. About 3,100 people have died from flu this season. The number of pediatric deaths rose to five, up from two the week before.

Doctors say they expect to see an increase in flu cases for at least the next several weeks, with illnesses not leveling off until the end of January or possibly February.

“Just looking at the trajectory of the curve, it’s really a pretty sharp increase that we’re seeing, and it’s not anywhere close to peaking or leveling off,” said Dr. Daniel Kuritzkes, a senior infectious disease physician at Mass General Brigham in Boston.