ICD-10 Code B10.09 – Other human herpesvirus encephalitis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code B10.09 – Other human herpesvirus encephalitis
What it is
B10.09 identifies encephalitis caused by a human herpesvirus other than the more commonly coded types. Use it when documentation specifically links the brain infection to another herpesvirus.
Clinical signs
Clinical features vary; refer to documentation. Encephalitis commonly presents with altered mental status, fever, headache, seizures, or focal neurologic findings, but the causal virus must be identified in the record.
When to use this code
Use B10.09 when the provider documents encephalitis due to another human herpesvirus and does not specify a different herpesvirus code. It is appropriate for confirmed viral encephalitis where the organism is named in the chart. Check documentation if the record only says “viral encephalitis” or lists herpesvirus without further detail.
Do not use for
Do not use this code for encephalitis caused by a different specified herpesvirus or when the diagnosis is not confirmed. If documentation is nonspecific, check documentation rather than assuming B10.09.
Coding tip
Assign the code only when the provider clearly identifies “other human herpesvirus” as the cause of encephalitis.