Unspecified viral encephalitis

This code represents an acute inflammation of the brain caused by a viral infection when the specific viral etiology is not identified. Patients typically present with fever, headache, altered mental status, and neurological deficits, but the causative virus remains unknown or unconfirmed.

This code is appropriate when documentation clearly indicates a diagnosis of viral encephalitis, but the specific viral agent (e.g., herpes simplex, West Nile, enterovirus) has not been determined or definitively ruled out. It is used when the provider has diagnosed encephalitis of presumed viral origin, but further specificity is lacking.

• Avoid using this code if a specific viral agent is identified; instead, use the more specific code from categories A83-A85.
• Query the provider for clarification if the documentation mentions "encephalitis" without specifying viral or other causes.
• Sequence this code as the primary diagnosis when it is the reason for the encounter or hospitalization.