2026 ICD-10-CM Diagnosis Code A81.89Other atypical virus infections of central nervous system

ICD-10-CM Codes›A00–B99›A80-A89›A81

ICD-10-CM A81.89
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A81.89 is a billable ICD-10-CM diagnosis code for other atypical virus infections of central nervous system. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 974 through 976. Coders also document this condition as variably protease sensitive prionopathy. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified CNS infection and poliomyelitis and Viral infection.

Code Identity

ICD-10-CM Code
A81.89
Billable Status
Yes — Valid for Submission
Code Describes
Other atypical virus infections of central nervous system
Short Description
Other atypical virus infections of central nervous system
Same as the full description in the CMS dataset.
Parent Code
A81.8
Other atypical virus infections of central nervous system

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA80-A89Viral and prion infections of the central nervous system
CategoryA81Atypical virus infections of central nervous system
This CodeA81.89Other atypical virus infections of central nervous system

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Variably protease sensitive prionopathy

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
      • prion, central nervous system
        • specified NEC
    • Infection, infected, infective(opportunistic)
      • atypical
        • virus
          • specified type NEC
    • Infection, infected, infective(opportunistic)
      • slow virus
        • specified NEC
    • Infection, infected, infective(opportunistic)
      • virus, viral NOS
        • central nervous system
          • atypical
            • specified NEC
    • Infection, infected, infective(opportunistic)
      • virus, viral NOS
        • central nervous system
          • slow virus
            • specified NEC
    • Infection, infected, infective(opportunistic)
      • virus, viral NOS
        • slow
          • specified NEC

Clinical ClassificationClinical

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

CCSR NVS003
Other specified CNS infection and poliomyelitis
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR INF008
Viral infection
Default principal diagnosis: inpatient No · outpatient No

Patient EducationClinical

Neurologic Diseases

The brain, spinal cord, and nerves make up the nervous system. Together they control all the workings of the body. When something goes wrong with a part of your nervous system, you can have trouble moving, speaking, swallowing, breathing, or learning. You can also have problems with your memory, senses, or mood.

Read the full article at MedlinePlus

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

Convert A81.89 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
046.79 Prion dis of CNS NEC/NOS
Approximate The match is approximate rather than exact.
ICD-9-CM
046.8 Cns slow virus infec NEC
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About A81.89Overview

Is A81.89 (Other atypical virus infections of central nervous system) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report other atypical virus infections of central nervous system on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does A81.89 group to?

When other atypical virus infections of central nervous system is the principal diagnosis on an inpatient stay, it groups to MS-DRG 974, 975, 976, with relative weights from 0.8945 to 2.8860 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of A81.89?

Under the General Equivalence Mappings, other atypical virus infections of central nervous system converts to ICD-9-CM 046.79 (prion dis of CNS NEC/NOS) and 046.8 (cns slow virus infec NEC). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.