2027 ICD-10-CM Diagnosis Code A81Atypical virus infections of central nervous system

ICD-10-CM Codes›A00–B99›A80-A89›A81

ICD-10-CM A81
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

A81 is a non-billable ICD-10-CM category code for atypical virus infections of central nervous system, so it cannot be submitted on claims. Use a more specific code from this category instead, such as A81.00, A81.01, A81.09, and A81.1.

Code Identity

ICD-10-CM Code
A81
Billable Status
No — Non-Billable Category
Code Describes
Atypical virus infections of central nervous system
Short Description
Atypical virus infections of central nervous system
Same as the full description in the CMS dataset.
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
CategoryA81Atypical virus infections of central nervous system
This CodeA81Atypical virus infections of central nervous system

Specific Coding for Atypical virus infections of central nervous systemOverview

Non-specific codes like A81 require more characters. Use one of these billable codes instead:

  • A81.0 for Creutzfeldt-Jakob disease

  • Use A81.00 for Creutzfeldt-Jakob disease, unspecified

  • Use A81.01 for Variant Creutzfeldt-Jakob disease

  • Use A81.09 for Other Creutzfeldt-Jakob disease

  • Use A81.1 for Subacute sclerosing panencephalitis

  • Use A81.2 for Progressive multifocal leukoencephalopathy

  • A81.8 for Other atypical virus infections of central nervous system

  • Use A81.81 for Kuru

  • Use A81.82 for Gerstmann-Straussler-Scheinker syndrome

  • Use A81.83 for Fatal familial insomnia

  • Use A81.89 for Other atypical virus infections of central nervous system

  • Use A81.9 for Atypical virus infection of central nervous system, unspecified

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to A81: its own notes plus those printed at block A80-A89 and Chapter 1. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

On A81 itself
  • diseases of the central nervous system caused by prions
From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • diseases generally recognized as communicable or transmissible

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From Block A80-A89 Viral and prion infections of the central nervous system applies to 48 codes
  • postpolio syndrome (G14)
  • sequelae of poliomyelitis (B91)
  • sequelae of viral encephalitis (B94.1)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • carrier or suspected carrier of infectious disease (Z22.-)
  • certain localized infections - see body system-related chapters
  • infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
  • infectious and parasitic diseases specific to the perinatal period (P35-P39)
  • influenza and other acute respiratory infections (J00-J22)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

On A81 itself
From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • code to identify resistance to antimicrobial drugs (Z16.-)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

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.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About A81Overview

What is the ICD-10 code for atypical virus infections of central nervous system?

A81 is the ICD-10-CM category for atypical virus infections of central nervous system, but it is a non-billable header: claims need a more specific code from this category, listed on this page.

Is A81 (Atypical virus infections of central nervous system) a billable code?

No. This is a category header that groups the codes for atypical virus infections of central nervous system, and headers cannot be submitted on claims. Claims for atypical virus infections of central nervous system need a more specific code from this category, such as A81.00, A81.01, and A81.09.

Can A81 be reported with G14?

Not as a rule. The Excludes1 note at block A80-A89, which applies to A81, lists "postpolio syndrome (G14)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).

Does A81 need an additional code?

When the condition applies, yes. The Use Additional Code note reads: code, if applicable, to identify: dementia with anxiety (F02.84, F02.A4, F02.B4, F02.C4); dementia with behavioral disturbance (F02.81-, F02.A1-, F02.B1-, F02.C1-); dementia with mood disturbance (F02.83, F02.A3, F02.B3, F02.C3); dementia with psychotic disturbance (F02.82, F02.A2, F02.B2, F02.C2); dementia without behavioral disturbance (F02.80, F02.A0, F02.B0, F02.C0); and 1 more listed in the Instructional Notes section. The additional code is reported after A81.