2026 ICD-10-CM Diagnosis Code A89Unspecified viral infection of central nervous system

ICD-10-CM Codes›A00–B99›A80-A89›A89

ICD-10-CM A89
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A89 is a billable ICD-10-CM diagnosis code for unspecified viral infection 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 viral infection of central nervous system. 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
A89
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified viral infection of central nervous system
Chapter
A80-A89
Viral and prion infections of the central nervous system

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA80-A89Viral and prion infections of the central nervous system
CategoryA89Unspecified viral infection of central nervous system
This CodeA89Unspecified viral infection of central nervous system

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Viral infection of central nervous system

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.

    • Infection, infected, infective(opportunistic)
      • virus, viral NOS
        • central nervous system

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 A89 to ICD-9-CMHistory

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

ICD-9-CM
049.9 Viral encephalitis NOS
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 A89Overview

Is A89 (Unspecified viral infection of central nervous system) a billable code?

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

What MS-DRG does A89 group to?

When unspecified viral infection 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 A89?

Under the General Equivalence Mappings, unspecified viral infection of central nervous system converts to ICD-9-CM 049.9 (viral encephalitis NOS). The mapping is approximate, so confirm the match fits the documentation.

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.