A86 Unspecified viral encephalitis
The ICD-10-CM code for Unspecified viral encephalitis is A86 (FY2026). It is a billable, claim-ready diagnosis code.
Classification
- Section
- A80-A89: Viral and prion infections of the central nervous system (A80-A89)
- Category A86
- 1 code (1 billable)
- FY2026 Status
- Stable since FY2024
Also Known As
ICD-10-CM Alphabetic Index entries that lead to A86:
- Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute) › postviral NEC
- Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute) › viral, virus
- Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute) › endemic (viral)
- Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute) › acute
- Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute) › epidemic NEC (viral)
- Meningoencephalitis › infectious (acute) (viral)
- Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute) › infectious (acute) (virus) NEC
- Meningoencephalitis › acute NEC
Inclusion Terms
- Viral encephalomyelitis NOS
- Viral meningoencephalitis NOS
U.S. Hospital Utilization
- An estimated 3,220 U.S. inpatient stays in 2023 included A86 among the documented diagnoses.
- 1,300 stays listed it as the principal diagnosis.
Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.
Official Coding Guidelines
HIV Infections (TOC entry)a. Human Immunodeficiency Virus (HIV) Infections .............................................................. 19
Infectious agents causing diseases in other chapters (TOC)b. Infectious agents as the cause of diseases classified to other chapters ................................. 22
Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026