A81 – Atypical virus infections of central nervous system
ICD-10-CM 2027 diagnosis code · Viral and prion infections of the central nervous system
ICD-10-CM code
A81
- Code
A81(claims format:A81)- Description
- Atypical virus infections of central nervous system
- Billable
- No – use a more specific code below
- Valid for
- Dates of service October 1, 2026 – September 30, 2027 (FY2027)
- Chapter
- 1. Certain infectious and parasitic diseases (A00-B99)
- Block
- A80-A89 Viral and prion infections of the central nervous system
Billable codes under A81
A81 is a header code and cannot be used on claims. Choose the most specific code:
- A81.0 – Creutzfeldt-Jakob diseaseHeader (more codes below)
- A81.1 – Subacute sclerosing panencephalitisBillable
- A81.2 – Progressive multifocal leukoencephalopathyBillable
- A81.8 – Other atypical virus infections of central nervous systemHeader (more codes below)
- A81.9 – Atypical virus infection of central nervous system, unspecifiedBillable
Notes for A81
Includes:
- diseases of the central nervous system caused by prions
Use additional code:
- 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)
- mild neurocognitive disorder due to known physiological condition (F06.7-)
Notes inherited from parent codes
Instructional notes at a category or block level apply to every code below it.
Block A80-A89
Frequently asked questions
What is ICD-10 code A81?
A81 is the ICD-10-CM code for atypical virus infections of central nervous system, in the block A80-A89 (Viral and prion infections of the central nervous system).
Is A81 a billable code?
No. A81 is a header code with more specific child codes; report one of the billable codes listed above.
Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.