Deadly Flu Complication On The Rise Among Children, Stanford Researchers Warn

A rare but deadly complication of the flu is increasing among young children, Stanford Medicine scientists warned.

A study, published on Wednesday in JAMA, described the complication, called influenza-associated acute necrotizing encephalopathy (ANE), as a form of brain inflammation that typically occurs in response to a virus like influenza.

The condition can lead to lasting neurological problems and brain damage. What's more, new findings in the study, led by Molly Wilson-Murphy, Rachel Walsh and dozens of other researchers across the nation, suggest that this complication is often fatal for the children who contract it, despite intensive treatment.

During the 2024 to 2025 flu season, doctors at large pediatric centers reported an alarming number of children who fell ill with ANE, according to the study.

That initial rise in cases inspired Wilson-Murphy and her colleagues at Stanford University and other institutions to begin collecting data on children who had contracted ANE between 2023 and 2025. What they found was shocking.

A study analyzing data from 41 patients across 23 U.S. pediatric hospitals found that ANE carries a significant risk of severe outcomes, such as death.

“While rare, ANE is potentially devastating and can progress very quickly. It is incredibly important for providers to be able to recognize ANE and to act immediately, as rapid treatment may save lives and minimize long-term difficulties,” Wilson-Murphy said, according to a news release.

According to the study, 27 percent of the children who were admitted to the hospital with the disease died, with almost all deaths occurring within three days of symptom onset, often due to brain herniation, during which brain matter pushes through the skull.

“It’s really getting through those first seven days that is critical,” Keith Van Haren, a pediatric neurologist at Stanford’s Lucille Packard Children’s Hospital who co-authored the study, told Mercury News. “Getting kids through that first week, which is really perilous, gives them a chance at having a decent outcome.”

The study found that kids who survived the first week were able to survive the disease overall.

However, the study found that among 30 survivors observed, many continued to experience neurological issues such as epilepsy three months later. Only 43 percent had regained the ability to walk without assistance.

“The recovery from acute necrotizing encephalopathy is comparable to that of a traumatic brain injury,” Van Haren told the newspaper.

Symptoms of ANE can be hard to detect and often come with the onset of flu symptoms. Children who contract the complication will often exhibit sudden changes in behavior or alertness. They may become extremely drowsy during the day.

Parents are advised to rush their children to an emergency room if they feel something isn't right. Rapid response is key to survival, according to the study.

“The symptoms can develop incredibly quickly,” Van Haren said. “It’s possible to go from drowsy to life-threatening in a matter of a couple of hours.”

While the cause of the complication is a mystery, the study's authors found that susceptibility to influenza was a huge risk factor.

Of the 41 patients included in the study, only six had received an age-appropriate flu vaccine for the season during which they developed ANE. Only one of the 11 children studied who died of the complication had received a flu shot.

Therefore, the authors maintain that vaccination is key to helping prevent ANE.

“There is still so much we have yet to learn about ANE, but we hope this study has helped raise awareness and pave the way for more surveillance and recognition and, ultimately, to advances in treatment,” says Wilson-Murphy.