ICD-10 Code A84.8 – Other tick-borne viral encephalitis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A84.8 – Other tick-borne viral encephalitis
What it is
A84.8 identifies tick-borne viral encephalitis that does not fit a more specific ICD-10 category. It refers to viral inflammation of the brain linked to tick exposure, with the exact virus or subtype not otherwise specified.
Clinical signs
Clinical features vary; refer to documentation. Typical encephalitis findings may include fever, headache, altered mental status, confusion, seizures, or focal neurologic deficits, especially after a tick bite or exposure in an endemic area.
When to use this code
Use A84.8 when the provider documents tick-borne viral encephalitis but does not identify a more specific organism or subtype. It also fits when the record states another or unspecified tick-borne viral encephalitis and no narrower code is supported by the chart.
Check documentation for the confirmed diagnosis, since suspected infection, tick bite alone, or nonspecific viral illness does not support this code. Code the encephalitis only when the clinician links the neurologic illness to tick-borne viral infection.
Do not use for
Do not use this code for bacterial meningitis, nonviral encephalitis, or tick bites without encephalitis. If the record names a different tick-borne viral encephalitis type, use the more specific ICD-10 code instead.
Coding tip
Code from the provider’s final diagnosis and choose the most specific tick-borne encephalitis code available; otherwise, use A84.8 only when documentation supports an unspecified or other type.