Flu Cases Are Surging

This flu season has been particularly brutal, and it isn’t showing signs of letting up.Since October, there have been at least 24 million cases in the United States.The Centers for Disease Control and Prevention has estimated that there have been as many as 650,000 hospitalizations, which would make it the highest hospitalization level since 2017.

Many parts of the country are reporting “high” or “very high” flu rates.The high case counts right now are striking, given that this is the time of year when flu typically starts to slow down, said Dr.Susan R.

Russell, medical director at the medical intensive-care unit at Northwestern Memorial Hospital in Chicago.But Dr.

Russell said she was still seeing a flood of patients in the hospital sick with the flu.Dr.Donald Dumford, an infectious-disease doctor at the Cleveland Clinic, said, “A couple of weeks ago, I was saying, ‘Oh, we’ve hit our peak, it’s going to start going down.’”“And then I got fooled,” he added.It’s not entirely clear why the current flu season has been so severe.

Doctors said vaccination rates have not been as high as they would like to see: Roughly 46 percent of children and a similar share of adults have received a flu vaccination so far this season, according to preliminary C.D.C.data.

Flu shots reduce the chance of infection, and might also help limit the spread of the virus to others.And some share of the cases could be a lingering consequence of pandemic lockdowns, when transmission of many common viruses slowed down as people practiced social distancing, Dr.Russell said.

Our immune systems may still be out of practice after not having to fend off respiratory diseases during that time.Some people are at high risk of becoming seriously ill and developing complications from an infection from the flu.This includes people who are very young or very old, or who have underlying lung or neurological disorders.

Those with obesity, heart disease or high blood pressure are...