ICD-10 Code A84.81 – Powassan virus disease (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A84.81 – Powassan virus disease
What it is
A84.81 identifies Powassan virus disease, a tick-borne viral infection. Use it when documentation names Powassan virus illness or encephalitis caused by Powassan virus.
Clinical signs
Clinical features vary; refer to documentation. Reported findings may include fever, headache, vomiting, confusion, weakness, seizures, or other neurologic signs consistent with central nervous system involvement.
When to use this code
Use A84.81 when the provider documents Powassan virus disease, Powassan virus encephalitis, or a confirmed infection due to this virus. It is appropriate for encounters focused on diagnosis, evaluation, or management of the documented illness. Check documentation if the record only notes tick exposure or suspected arboviral infection.
Do not use for
Do not assign this code for nonspecific fever, tick bite alone, or another confirmed viral encephalitis. If the chart does not clearly identify Powassan virus disease, check documentation.
Coding tip
Code from the provider’s final diagnosis, not from exposure history or preliminary testing alone.