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.
Flu 2025: Where is it spreading?
An epidemic of flu happens every year in the U.S., from October to as late as May, but the virus is taking off faster than usual this season.
New states reporting high levels of flu include California, Nevada, Missouri, Arkansas, Alabama and Florida.
Several states that were already in the CDC’s “very high” category are now at the top end of the range. Those states are New York, New Jersey, South Carolina, Louisiana and Colorado.
Dr. Jennifer Goebel, attending physician at South Shore University Hospital, Northwell in New York, said the hospital began seeing a rush of flu cases around Thanksgiving, maybe even a bit earlier.
“I don’t remember seeing flu cases this early and in this many numbers,” Goebel said. “It seems worse. Just a tremendous amount of volume.”
Dr. Donald Yealy, the chief medical officer of the UPMC health system, which has hospitals in Pennsylvania, Maryland and New York, said that for the past two weeks, he’s seen “a dramatic uptick” in the number of people coming in with acute respiratory infections.
“The biggest set of those are people with suspected influenza,” Yealy said. “And of those that we have adequate testing, it’s disproportionately influenza A.”
Who is hardest hit this flu season?
Doctors say infants and young children through age 4 have been among those hit hardest.
As cases rise, however, Dr. Lauren Siewny, the medical director of Duke University Hospital Emergency Department in North Carolina, said school-aged children and young adults are also coming in sick with the flu.
Older adults and people with chronic conditions are more likely to need hospitalization, Siewny added. Beds are also tight, she said, with cases of Covid and RSV overlapping with flu patients.
“We have built-in plans for these surges, and we prioritize the sickest patients first,” Siewny said.
Yealy said they’re seeing the flu hit all age groups, although the vast majority of people who require admission or advanced care are unvaccinated.
They’re also seeing a small uptick in Covid, norovirus and RSV cases, but the majority of cases that come in are the flu.
“We’re in the winter viral season,” he said.
Goebel, of South Shore University Hospital, also said they’re seeing cases across all age groups, adding, “We’re really just kind of seeing it across the board.”
Is the new variant a ‘super flu’?
The dominant strain right now is Influenza A — specifically a fast-spreading, mutated H3N2 strain called “subclade K.” H3N2 generally is thought to cause more severe illness, which may explain the sudden rise in hospitalizations.
The mutated strain, dubbed by some as “super flu,” emerged over the summer and includes changes to a key surface protein, which can make it harder for the immune system to recognize the virus. It’s also being blamed for a severe and early flu season in the United Kingdom and Japan.
Dr. Wenqing Zhang, who heads the World Health Organization’s unit for global respiratory threats, wrote in a recent blog post that current data don’t suggest an increase in disease severity from the new strain.
“Although the genetic shift makes a notable evolution in the virus,” Zhang wrote.
What are the flu variant symptoms?
Dr. Molly Fleece, associate professor in the division of infectious diseases at the University of Alabama at Birmingham, said symptoms have been pretty much the same compared to previous flu seasons.
“Symptoms start acutely,” she said. “People have higher fever, shaking, chills, cough, shortness of breath and muscle aches.”
Symptoms can be more severe, especially if a person is unvaccinated, Fleece said. Older adults and those with underlying medical conditions have also reported more serious complications, including pneumonia, muscle breakdown and seizures.
Goebel said patients are also reporting headaches or fatigue, and in some cases nausea, vomiting and diarrhea.
“If patients are having shortnesss of breath, if patients are having high fever despite taking Tylenol and Motrin around the clock or really any concerns at all, we advise them to seek medical attention,” she said.
Should I get my flu shot?
Doctors say it’s not too late to get a shot.
This year’s flu shot has a component of H3N2, although it doesn’t match perfectly with the mutated strain, Fleece said. “That’s because the subclade mutated and spread after the vaccines were already selected for the year.”
But that doesn’t mean the vaccine isn’t effective, she added.
“It may mean that more people will be susceptible to getting the flu … but we know from historical data the vaccine is still very effective at preventing severe illness, hospitalization and death.”
Yealy said the shot “essentially arms your body with the appropriate response before you get infected.”
“This year’s seasonal vaccine can help provide protection,” he said.
Other winter viruses circulating
Flu is dominant right now but Covid infections are slowly increasing nationwide, according to data from WastewaterScan, an academic program through Stanford University in partnership with Emory University. Covid levels are high in the South, Northeast and Midwest.
Norovirus infections, which spiked in late November, are still high and continuing to rise.
Respiratory syncytial (RSV) is starting to take off, especially in the South, the WastewaterScan data show.
Doctors say it’s possible to have more than one viral infection at a time, a situation that can cause worse illness.
“Having one virus doesn’t actually shun another one off,” Yealy said. “The bigger issue is having one of the respiratory viruses and it worsening a second condition.”
