ICD-10 Code A89 – Unspecified viral infection of central nervous system (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A89 – Unspecified viral infection of central nervous system
What it is
A89 identifies a viral infection affecting the central nervous system when the specific virus or exact CNS diagnosis is not documented. Use it for nonspecific viral CNS illness that cannot be classified more precisely.
Clinical signs
Clinical features vary; refer to documentation. Patients may have neurologic symptoms such as headache, fever, altered mental status, meningismus, seizures, or focal deficits, but the record should support a viral CNS infection.
When to use this code
Use A89 when the provider documents a viral infection of the central nervous system without naming the organism or a more specific condition. It also fits when the chart confirms viral CNS involvement, but details are incomplete. If encephalitis, meningitis, or another specific diagnosis is documented, code that condition instead.
Do not use for
Do not use this code for bacterial, fungal, or parasitic CNS infections, or for viral illnesses limited to non-CNS sites. Check documentation if the provider names encephalitis, meningitis, or another more specific CNS disorder.
Coding tip
Code the most specific CNS infection documented, and query the provider if the record only says “viral CNS infection” without further detail.