Overview

• A Stanford-led JAMA study identified 41 cases of influenza-associated acute necrotizing encephalopathy in U.S. children between October 2023 and May 2025, a marked increase over the typical one or two cases every few years.
• The condition triggered rapid brain swelling and hyperinflammation, resulting in a 27% fatality rate and leaving 63% of survivors with moderate to severe disability three months after illness onset.
• Just 16% of affected children had received seasonal flu vaccines, compared with roughly 50% pediatric vaccination coverage nationwide during recent seasons.
• Rapid intervention in pediatric intensive care units—including high-dose steroids, plasma exchange and advanced neurocritical support—was linked to better survival and functional recovery.
• Physicians and public health experts are calling for mandatory case reporting and multiyear national surveillance to accurately track and prevent future acute necrotizing encephalopathy outbreaks.