Rare but Severe Flu Complication Raises Concern Ahead of Flu Season
Influenza remains one of the most common and serious viral infections worldwide. Each year, millions of people are infected, and hundreds of thousands require hospital care. In the United States alone, between 47 and 82 million flu cases were reported between October 2024 and May 2025, resulting in as many as 1.3 million hospitalizations, according to preliminary estimates from the Centers for Disease Control and Prevention (CDC). While most patients recover, influenza can sometimes lead to unexpected and life-threatening complications.
One such complication is acute necrotizing encephalopathy (ANE)—a rare but devastating condition, especially in children. A recent study published in JAMA has brought renewed attention to this disorder, showing that despite treatment, ANE carries a mortality rate of nearly 27%.
Understanding Complications from the Flu
Most individuals who contract influenza experience fever, headache, sore throat, fatigue, and other uncomfortable but temporary symptoms. However, certain groups are more likely to develop severe complications. These include adults over 65, children under 2, pregnant women, and people with chronic illnesses such as diabetes, lung disease, heart conditions, or weakened immune systems.
Complications can range from pneumonia and sinus infections to neurological problems and the worsening of existing health conditions. Among the most serious is ANE, which directly impacts the brain.
What Is Acute Necrotizing Encephalopathy?
ANE is a rare disorder triggered by viral infections, most often influenza. It causes severe inflammation and swelling in the brain, which can lead to seizures, coma, long-term disability, or death. Although uncommon, the consequences are alarming due to the speed and severity with which the condition progresses.
The new study reviewed 41 pediatric cases of flu-related ANE across the U.S. between October 2023 and May 2025. The median age of affected children was just five years old, and strikingly, most had been healthy prior to falling ill. Of those whose vaccination history was known, only 16% had received that season’s flu vaccine.
All children in the study developed altered brain function. Nearly 70% experienced seizures, while many showed abnormal liver function and blood clotting issues. Despite intensive treatments—such as steroids and immunoglobulins—11 children died, with death often occurring within three days of symptom onset. Brain swelling was the primary cause, as it compressed areas essential for breathing and heart function. Among survivors, nearly two-thirds were left with moderate or severe disability.
Prevention and the Role of Vaccination
Researchers stress that while it is not fully understood why some children develop ANE and others do not, vaccination plays a protective role. The majority of children who died in the study had not been vaccinated against the flu. Although vaccination cannot guarantee protection, it reduces the likelihood of severe illness and complications, including ANE.
Health experts urge families to ensure that all eligible members, especially children, receive the flu vaccine each fall. The CDC recommends vaccination for everyone over six months of age. In addition to vaccination, preventive measures such as good hand hygiene, staying home when sick, and masking in crowded indoor spaces during flu season can further reduce risks.
What Families Should Know Moving Forward
The key message from this research is clear: influenza should not be underestimated. Even in healthy children, the virus can lead to severe outcomes such as ANE. Parents should treat vaccination as the first line of defense, while also practicing everyday precautions to limit the spread of respiratory viruses.
As the flu season approaches, raising awareness of complications like ANE is vital. Early recognition, timely medical care, and prevention through vaccination remain the most effective strategies to protect children and communities.
