Arthropod-borne viral encephalitis, unspecified

This code represents an inflammation of the brain caused by a viral infection transmitted by arthropods (e.g., mosquitoes, ticks), where the specific type of arthropod-borne virus is not identified in the medical record. It indicates a diagnosis of viral encephalitis with an arthropod vector, but without further etiological specificity.

Use this code when documentation confirms a diagnosis of viral encephalitis and explicitly states an arthropod vector, but the specific virus (e.g., St. Louis, Eastern equine) is not documented. This code is appropriate when the physician has not specified the exact viral agent responsible for the encephalitis.

• Do not use if the specific arthropod-borne virus is known; instead, code to the specific viral encephalitis (e.g., A83.0 for Japanese encephalitis).
• Ensure documentation clearly links the encephalitis to an arthropod vector; otherwise, consider unspecified viral encephalitis (A86).
• Review the "Excludes1" note carefully to avoid co-coding with West Nile virus encephalitis.