ICD-10 Code A92.31 – West Nile virus infection with encephalitis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A92.31 – West Nile virus infection with encephalitis
What it is
This code identifies West Nile virus infection complicated by encephalitis, meaning inflammation of the brain caused by the virus. Use it when the record clearly documents both West Nile infection and encephalitis.
Clinical signs
Typical findings include fever, headache, altered mental status, confusion, and neurologic deficits. Clinical features vary; refer to documentation for confirmed encephalitis.
When to use this code
Use A92.31 when the clinician documents West Nile virus infection with encephalitis, or when encephalitis is specifically attributed to West Nile virus. Apply it from inpatient, outpatient, or emergency records if the diagnosis is confirmed in the chart.
Code it only when the documentation supports central nervous system involvement. If the note mentions West Nile virus without encephalitis, choose a different code and check documentation.
Do not use for
Do not use this code for uncomplicated West Nile virus infection, meningitis alone, or nonspecific viral illness. Check documentation when encephalitis is not clearly stated.
Coding tip
Look for explicit linkage between West Nile virus and encephalitis before assigning A92.31.