Written By: N. Lothungbeni Humtsoe | Updated : August 24, 2025 12:10 AM IST
Acute Necrotizing Encephalopathy: Influenza is a common illness that sweeps across countries, especially during the monsoon season. As flu season approaches in the United States, health experts are alarmed over a rare and severe flu which develops after viral infections that can affect even a healthy child.
According to reports, doctors are advising parents to remain alert, as several children across the United States have developed the life-threatening illnesses called Acute Necrotizing Encephalopathy (ANE), which cause brain swelling and extreme immune responses during the flu season.
The National Institute of Health (NIH) states, "Acute Necrotizing Encephalopathy (ANE) is a rare but distinctive type of acute encephalopathy with global distribution. Occurrence of ANE is usually preceded by a virus-associated febrile illness and is followed by rapid deterioration. However, the causal relationship between viral infections and ANE and the exact pathogenesis of ANE remain unclear; both environmental and host factors might be involved."
A case study, which is now published in the Journal of the American Medical Association (JAMA), states that during the 2024-2025 US influenza season, clinicians at large pediatric centers anecdotally reported an increased number of children with influenza-associated ANE, prompting this national investigation.
Keith Van Haren, MD, associate professor of neurology and neurological sciences and of paediatrics, was reported saying, "Acute Necrotizing Encephalopathy (ANE) is the most severe flu complication, but it's only the tip of the iceberg for what flu can do. Flu causes all kinds of complications, including other forms of brain swelling, as well as pneumonia and respiratory failure. Vaccines really do help protect wonderfully against all those complications."
The study examined 41 cases of ANE which occurred across the US between 2023 to 2025, an unusually high number linked to severe flu seasons. This rare complication of flu can cause brain swelling and also a runaway immune response, a combination that experts warn can be fatal.
Findings show that 27% of affected children died, and 63% of the survivors still had moderate to severe disability three months after they became sick.
Citing concerns about the rare complications of ANE, Thomas LaRocca, MD, PhD, a clinical assistant professor and a pediatric critical care medicine specialist at Packard Children's, said, "It is essential that doctors promptly identify patients with ANE to ensure that these children can receive rapid, intensive care at hospitals that offer advanced neurocritical care and have experts familiar with immunomodulating medications."
According to NIH, people with this condition show common symptoms of an infection, such as fever, cough, congestion, vomiting, and diarrhoea, for a few days. However, following the flu-like symptoms, an affected individual gradually develops neurological problems, such as seizures, hallucinations, difficulty coordinating movements (ataxia), or abnormal muscle tone. "Eventually, most affected individuals go into a coma, which usually lasts for a number of weeks. The condition is described as "acute" because the episodes of illness are time-limited," NIH states.
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Children under age 5 are most commonly affected by Acute Necrotizing Encephalopathy (ANE).
No, Acute Necrotizing Encephalopathy (ANE) is not the same as the common flu. It is a complication triggered by viral infections that attacks the brain and can become fatal.
