ICD-10 Code A84.89 – Other tick-borne viral encephalitis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A84.89 – Other tick-borne viral encephalitis
What it is
A84.89 identifies tick-borne viral encephalitis that does not fit a more specific ICD-10 category. Use it for documented viral brain inflammation linked to a tick exposure or tick-borne infection when the record is nonspecific.
Clinical signs
Typical features include fever, headache, altered mental status, and neurologic findings consistent with encephalitis. Clinical features vary; refer to documentation, and code only when the provider documents tick-borne viral encephalitis.
When to use this code
Use this code when the clinician documents other tick-borne viral encephalitis and no more specific encephalitis code applies. It may also fit cases described as tick-borne viral encephalitis without naming the exact virus. If the chart is unclear, check documentation before assigning A84.89.
Do not use for
Do not use A84.89 for bacterial meningitis, nonviral encephalitis, or a general tick bite without encephalitis. If the organism or encephalitis type is documented more specifically, code that diagnosis instead.
Coding tip
Confirm that the provider links the encephalitis to a tick-borne viral cause before coding A84.89.