Influenza-Associated Encephalopathy and Encephalitis in Children

This purpose of this Health Advisory is to inform clinicians about reports of pediatric influenza-associated encephalopathy and encephalitis (IAE), including four deaths nationally from acute necrotizing encephalopathy (ANE), a severe form of IAE. Centers for Disease Control and Prevention (CDC) has requested that local public health be notified about these conditions.  

ACTIONS REQUESTED OF CLINICIANS   

• At every opportunity, strongly recommend and administer influenza vaccine to all patients at least 6 months of age. 
• Initiate early antiviral treatment for patients of any age who are at increased risk for influenza-associated complications. 
• Consider IAE or ANE in pediatric patients who present with persistent fever and altered mental status. CSF may show normal WBCs with elevated protein. Providers should:   
  
  • Test for influenza. Retain and submit positive specimens to Alameda County Public Health Laboratory for subtyping and sequencing. 
  • Hold serum and CSF for possible further testing.  
  • Voluntarily report all suspected or confirmed IAE or ANE cases that have occurred since October 1, 2024 and meet the following criteria to Alameda County Public Health at (510) 267-3250: 
    • Age <18 years 
    • Admitted to an acute care hospital or pronounced dead in an emergency department between October 1, 2024, and May 30, 2025 
    • Laboratory-confirmed influenza virus infection within 14 days preceding hospital presentation, during hospitalization, or in respiratory specimens collected post-mortem
    • Documented neurologic abnormalities (meets one or more of the following):
      
      • Diagnosis of encephalopathy or encephalitis 
      • Neurologic signs or symptoms including but not limited to seizures, altered mental status, delirium, decreased level of consciousness, lethargy, hallucinations, or personality changes lasting >24 hours 
      • Neuroimaging abnormalities such as brain edema, brain inflammation, or brain lesions 
      • Electroencephalogram abnormalities 
      • Abnormal brain autopsy findings, if available, for children who died 
• Report laboratory-confirmed influenza-associated fatal pediatric cases (<18 years) to Alameda County Public Health at acutecd@acgov.org as soon as possible. 
  
  

For more information, please review the complete advisory.