While the hospitalization rates are highest among adults 65 and older, health officials said baby boomers — adults ages 50 to 64 — were the next most likely to be hospitalized.

“This is a change,” said Dan Jernigan, MD, director of the CDC’s Influenza Division. Young children are typically the second most likely to be hospitalized with flu.

Included in the updated numbers this week was news of seven more flu deaths among kids. So far this season, 37 children have died of the flu.

Flu activity has been higher in the U.S. for 9 weeks. Flu seasons typically last 16 to 20 weeks, putting the nation at the halfway point of its feverish and aching misery.

Jernigan pointed to a couple of reasons that middle-aged adults might be more likely to get the flu this season: biology and behavior.

How a person responds to the circulating flu depends, in part, on the first flu strains they were exposed to as children — an immune phenomenon called imprinting. Jernigan suspects that the flu strains that imprinted on baby boomers years ago are very different from the kinds that are going around now, making boomers more vulnerable.

They’re also less likely to get vaccinated. A 2015 study found that while almost three-quarters of adults over 65 get an annual flu shot, less than half of middle-aged adults do.

“It has been a tough flu season so far this year. While flu activity is starting to go down in some areas, it remains high in much of the U.S. and in some areas is still rising,” Jernigan said.

He said there were signs in California and some Western states — where the flu has packed hospitals — that the epidemic was slowing. In New York, on the other hand, there were indications that the season was just gaining steam.

“We would expect, at the end of this season, to have somewhere around this number,” he said.

If you are a healthy adult, meaning that you don’t have another medical condition like asthma or diabetes or pregnancy, you’re probably OK dealing with the flu at home, says William Schaffner, MD, an infectious disease specialist at Vanderbilt University in Nashville.

“Take lots of fluid. Force yourself to sit up every 15 or 20 minutes and sip on some water,” he says. “It’s very, very important, because as you become dehydrated and you’re horizontal, you’re more likely to develop the complication of pneumonia.”

Adults 65 and older; those who have a medical condition like heart disease or diabetes; pregnant women; and children under 5 should get to the doctor within 48 hours of their first symptoms. Doctors can prescribe antiviral medications that can lessen the chance of severe complications.

Symptoms that should send anyone — children or adults — for immediate medical attention include:

• Shortness of breath
• Difficulty breathing
• Chest pain
• A temperature of 103 F or higher and a fever that doesn’t come down over time or with medication.
• Ear pain (sometimes a sign in kids of a viral infection)

Schaffner says he would add another sign to the list: Flu causes a dry cough. If you instead develop a wet cough that begins to bring up green, yellow, or blood-streaked phlegm, it’s time to get to the hospital, since that can be a sign of pneumonia.

CDC Director Brenda Fitzgerald, MD, urged people with any symptoms of the flu, including headache, body aches, cough, and fever, to stay home. She also urged people to wash their hands frequently, especially if they’re caring for someone who’s sick, to prevent the spread of the virus.

The CDC recommends antiviral medications that can shorten how long the flu lasts and blunt its symptoms, especially when they are given at the first sign of illness. Health officials said they are aware that some of the medications are in short supply in some areas. Jernigan said it’s worth calling ahead to your pharmacy to make sure they’re in stock.