A81

Atypical virus infections of central nervous system

Not billable — category only FY2026 2025-10-01 → 2026-09-30

Exclusions 8 never code together

A80-A89block

Excludes1

postpolio syndrome (G14)G14
sequelae of poliomyelitis (B91)B91
sequelae of viral encephalitis (B94.1)B94.1

A00-B99chapter

Excludes1

certain localized infections - see body system-related chapters

Excludes2

carrier or suspected carrier of infectious disease (Z22.-)Z22.-
infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)O98.-
infectious and parasitic diseases specific to the perinatal period (P35-P39)P35-P39
influenza and other acute respiratory infections (J00-J22)J00-J22

Excludes1 — never code together. The excluded condition and this one are mutually exclusive.

Excludes2 — not included here, but the patient may have both. Code both when documented.

Instructional notes 10

A81code

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)F02.84 F02.84 F02.84 F02.A4 F02.A4 F02.A4 F02.B4 F02.B4 F02.B4 F02.C4 F02.C4 F02.C4
dementia with behavioral disturbance (F02.81-, F02.A1-, F02.B1-, F02.C1-)F02.81-F02.81-F02.81-F02.A1-F02.A1-F02.A1-F02.B1-F02.B1-F02.B1-F02.C1-F02.C1-F02.C1-
dementia with mood disturbance (F02.83, F02.A3, F02.B3, F02.C3)F02.83 F02.83 F02.83 F02.A3 F02.A3 F02.A3 F02.B3 F02.B3 F02.B3 F02.C3 F02.C3 F02.C3
dementia with psychotic disturbance (F02.82, F02.A2, F02.B2, F02.C2)F02.82 F02.82 F02.82 F02.A2 F02.A2 F02.A2 F02.B2 F02.B2 F02.B2 F02.C2 F02.C2 F02.C2
dementia without behavioral disturbance (F02.80, F02.A0, F02.B0, F02.C0)F02.80 F02.80 F02.80 F02.A0 F02.A0 F02.A0 F02.B0 F02.B0 F02.B0 F02.C0 F02.C0 F02.C0
mild neurocognitive disorder due to known physiological condition (F06.7-)F06.7-F06.7-F06.7-

A00-B99chapter

Includes

diseases generally recognized as communicable or transmissible

Use additional code

code to identify resistance to antimicrobial drugs (Z16.-)Z16.-

Index entries leading here filed at null

No alphabetic index entry points at this code.

Subordinate codes 5

A81.0 Creutzfeldt-Jakob disease A81.1 Subacute sclerosing panencephalitis A81.2 Progressive multifocal leukoencephalopathy A81.8 Other atypical virus infections of central nervous system A81.9 Atypical virus infection of central nervous system, unsp

Medications 5

80 Central Nervous System Infections drugs 693 Central Nervous System Diseases drugs 1336 Nervous System Diseases drugs 190 DNA Virus Infections drugs 131 Nervous System Neoplasms drugs

MED-RT files conditions by MeSH, which carves the world differently from ICD-10. These are name matches on this code's description, offered as candidates — not as an assertion that they are this code.

Additional references

AHA Coding Clinic® Licence required

Official coding advice for this code. Published by the American Hospital Association. Not included in this installation.

Risk adjustment

Maps to no condition category in any loaded model.

Presence is a property of the code. Untick a model to hide it everywhere.

This code

Billable: no
Code set: FY2026
Block: A80-A89
Subordinate: 5

Present FY2024–FY2027.