ICD-10 Code A83.8 – Other mosquito-borne viral encephalitis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A83.8 – Other mosquito-borne viral encephalitis
What it is
A83.8 identifies mosquito-borne viral encephalitis that is not classified elsewhere. Use it for viral inflammation of the brain linked to mosquito transmission when the specific agent is not named in the record.
Clinical signs
Clinical features vary; refer to documentation. Encephalitis may present with fever, headache, altered mental status, seizures, or focal neurologic findings, but you should code only when the record supports a mosquito-borne viral cause.
When to use this code
Use this code when the provider documents other mosquito-borne viral encephalitis and does not identify a more specific virus. It also fits cases where the chart confirms mosquito transmission and encephalitis, but the organism is not otherwise classified. Check documentation if the diagnosis is uncertain or only suspected.
Do not use for
Do not use A83.8 for non-viral encephalitis, encephalopathy, or meningitis without encephalitis. Also avoid it when the record names a different mosquito-borne disease or a more specific encephalitis code applies.
Coding tip
Assign the code only when both mosquito-borne transmission and viral encephalitis are documented, and verify whether a more specific diagnosis is available.