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Pediatric Influenza-Associated Encephalopathy and Acute Necrotizing Encephalopathy - United States, 2024-25 Influenza
Insights
Severe influenza-associated encephalopathy (IAE), including acute necrotizing encephalopathy (ANE), caused child deaths. Annual influenza vaccination is crucial for preventing these severe neurologic complications in children.
Area of Science:
- Pediatric neurology
- Infectious diseases
- Public health surveillance
Background:
- Severe influenza-associated encephalopathy (IAE), including acute necrotizing encephalopathy (ANE), has been reported in children.
- No established national surveillance system exists for pediatric IAE.
- The 2024-25 influenza season was severe, with a high number of pediatric influenza-associated deaths.
Purpose of the Study:
- To describe the characteristics and outcomes of pediatric IAE and ANE cases during the 2024-25 influenza season.
- To assess the role of influenza vaccination in preventing severe IAE/ANE.
Main Methods:
- CDC requested U.S. clinicians and health departments to report suspected pediatric IAE cases.
- Cases were categorized as IAE (including ANE) or other influenza-associated neurologic disease.
- Data on patient demographics, clinical presentation, outcomes, and vaccination status were collected.
Main Results:
- Of 192 suspected cases, 109 met IAE criteria (37 ANE, 72 other IAE), and 82 were classified as other influenza-associated neurologic disease.
- The median age for IAE cases was 5 years; 55% were previously healthy.
- Mortality was 19% for IAE and 41% for ANE. Only 16% of eligible children with IAE were vaccinated.
Conclusions:
- IAE and ANE are severe, potentially fatal, neurologic complications of influenza in children.
- Healthcare providers should consider IAE in children with encephalopathy during influenza season.
- Annual influenza vaccination is recommended for all children to prevent influenza and its severe neurologic sequelae.
Abstract:
In January 2025, CDC received several reports of deaths among children aged <18 years with a severe form of influenza-associated encephalopathy (IAE) termed acute necrotizing encephalopathy (ANE). Because no national surveillance for IAE currently exists, CDC requested notification of U.S. pediatric IAE cases from clinicians and health departments during the 2024-25 influenza season, a high-severity season with a record number of pediatric influenza-associated deaths. Among 192 reports of suspected IAE submitted to CDC, 109 (57%) were categorized as IAE, 37 (34%) of which were subcategorized as ANE, and 72 (66%) as other IAE; 82 reports did not meet IAE criteria and were categorized as other influenza-associated neurologic disease. The median age of children with IAE was 5 years and 55% were previously healthy, 74% were admitted to an intensive care unit, and 19% died; 41% of children with ANE died. Only 16% of children with IAE who were vaccination-eligible had received the 2024-25 influenza vaccine. Health care providers should consider IAE in children with encephalopathy or altered level of consciousness and a recent or current febrile illness when influenza viruses are circulating. Annual influenza vaccination is recommended for all children aged ≥6 months to prevent influenza and associated complications, potentially including severe neurologic disease such as IAE and ANE.
