2026 ICD-10-CM Diagnosis Code A84.81Powassan virus disease

ICD-10-CM Codes›A00–B99›A80-A89›A84

ICD-10-CM A84.81
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A84.81 is a billable ICD-10-CM diagnosis code for Powassan virus disease. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). Coders also document this condition as invasive viral infectious disease. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Encephalitis and Viral infection.

Code Identity

ICD-10-CM Code
A84.81
Billable Status
Yes — Valid for Submission
Code Describes
Powassan virus disease
Short Description
Powassan virus disease
Same as the full description in the CMS dataset.
Parent Code
A84.8
Other tick-borne viral encephalitis

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA80-A89Viral and prion infections of the central nervous system
CategoryA84Tick-borne viral encephalitis
This CodeA84.81Powassan virus disease

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Invasive viral infectious disease
  • Neuroinvasive Powassan encephalitis virus infection
  • Powassan encephalitis virus infection
  • Powassan virus non-neuroinvasive disease

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Disease, diseased
      • viral, virus
        • Powassan
    • Encephalitis(chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
      • Powassan

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NVS002
Encephalitis
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR INF008
Viral infection
Default principal diagnosis: inpatient No · outpatient No

Patient EducationClinical

Tick Bites

Ticks are small parasites. They may look like insects, but they have eight legs and are related to spiders. Ticks feed on the blood of people and warm-blooded animals. There are many types of ticks in the United States, and they live in different parts of the country.

The full article covers:

  • What are ticks?
  • Why do I need to be worried about tick bites?
  • What happens if I get bitten by a tick?
  • How do I remove a tick?
  • When do I need to contact my health care provider about a tick bite?
  • How can I prevent tick bites?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code History & ChangesHistory

Replacement A84.81 replaces the following previously assigned code(s):

  • A84.8 - Other tick-borne viral encephalitis
FY 2021AddedAdded to the ICD-10-CM code setEffective October 1, 2020.
FY 2022–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About A84.81Overview

Is A84.81 (Other tick-borne viral encephalitis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report Powassan virus disease on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.