We all know influenza is a common and sometimes serious viral infection, but it’s worth a reminder as the flu season approaches, typically starting in October. Between October 2024 and May 2025, the United States saw an estimated 47 million to 82 million flu cases, leading to 610,000 to 1.3 million hospitalizations, according to preliminary data from the US Centers for Disease Control and Prevention. While most flu-related deaths occur in older adults, children can also be affected, with CDC estimates showing 37 to 199 deaths among children each flu season.Now, a new study published in JAMA has highlighted a rare yet severe complication that can affect children who contract the flu. Known as acute necrotizing encephalopathy (ANE), this condition carries a mortality rate of 27% even with intensive medical care, according to the research.What Is Acute Necrotizing Encephalopathy?Acute necrotizing encephalopathy (ANE) is a rare but serious brain disorder that can develop after a viral infection, most commonly influenza. It begins with a fever and quickly progresses to severe neurological problems, such as seizures and a reduced level of consciousness. Importantly, the condition is caused by the body’s inflammatory immune response to the virus, rather than the virus directly attacking the brain. Treatment typically involves supportive care and, in some cases, immunosuppressive therapies, but outcomes are often poor, with high rates of death and long-term brain damage.Symptoms of Acute Necrotizing EncephalopathyANE usually starts with symptoms of the initial viral infection, such as fever, cough, vomiting, and diarrhea, followed by rapid neurological decline, which may include:SeizuresConfusion, drowsiness, and altered consciousnessComa lasting for weeksProblems with movement (ataxia)Abnormal muscle toneHow Can Flu Lead to Acute Necrotizing Encephalopathy?According to the National Institutes of Health, the flu can trigger ANE through an overactive inflammatory response. In this scenario, the body’s immune system, activated by the virus, ends up damaging brain tissue rather than the virus directly affecting the brain. This process, often called a cytokine storm, leads to rapid swelling, inflammation, and tissue death in areas such as the thalamus, resulting in severe neurological symptoms like seizures and coma. Genetic factors may also make some children more vulnerable.The researchers collected data from US pediatric hospitals and public health agencies on cases of pediatric ANE treated between October 2023 and May 2025. They analyzed 41 children with influenza-related ANE. The median age was 5, and roughly three-quarters were previously healthy. Among those whose vaccination history was known, only 16% had received the flu vaccine that season.All of these children became seriously ill, and every patient developed encephalopathy, meaning altered brain function. Sixty-eight percent experienced seizures, and most had abnormal platelet counts, liver enzyme levels, and spinal fluid composition.The researchers emphasized a few key points:ANE is rare but extremely serious, with high risks of long-term illness or death, making early diagnosis and treatment critical.Most children affected were previously healthy.While a few vaccinated children also became ill, most cases and nearly all fatalities occurred in children who were not vaccinated that season.Why the Flu Vaccine MattersWhat is clear from this research is that getting the flu vaccine lowers the chance of catching the virus and of becoming seriously ill. The JAMA study also indicates that vaccination reduces the likelihood of developing ANE and the risk of dying from it. Both the study and an accompanying editorial stress the importance of everyone staying up-to-date with their flu shots.
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