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ICD-10 Code A86: Unspecified viral encephalitis

A86 is a billable ICD-10 diagnosis code used to classify Unspecified viral encephalitis in medical records and claims. You may see this code in hospital records, discharge summaries, insurance claims, encounter documentation, referrals, or other healthcare billing and coding records. ICD-10 codes are diagnosis classification codes used in healthcare records, reporting, coding workflows, and billing support. This code sits within the broader ICD-10 area for Certain infectious and parasitic diseases (A00-B99).

Reviewed by HealthAssure Clinical TeamUpdated 26 May 2026

What is this code?

ICD-10 codes are diagnosis classification codes used in healthcare records, reporting, coding workflows, and billing support. This code sits within the broader ICD-10 area for Certain infectious and parasitic diseases (A00-B99).

When is it used?

  • May be used when a clinician documents unspecified viral encephalitis in a patient's medical record.
  • May appear in hospital records, claims, referrals, and clinical documentation.
  • This code can be used as a clinically usable diagnosis entry in standardized coding workflows.

What it does not mean

  • A code alone does not explain severity, treatment plan, or outcome.
  • A medical code should not be treated as a substitute for a doctor's diagnosis or advice.

Code hierarchy

chapter
1Certain infectious and parasitic diseases (A00-B99)
block
A80-A89Viral and prion infections of the central nervous system
currentA80-A89

Official coding notes

Inclusion terms
  • Viral encephalomyelitis NOS
  • Viral meningoencephalitis NOS

Where you may see this code

You may see this code in hospital records, discharge summaries, insurance claims, encounter documentation, referrals, or other healthcare billing and coding records.

Related specialists

Infectious Disease SpecialistGeneral Physician

Coverage-related procedures and services

CPT 87483high
INFECTIOUS AGENT DETECTION BY NUCLEIC ACID (DNA OR RNA); CENTRAL NERVOUS SYSTEM PATHOGEN (EG, NEISSERIA MENINGITIDIS, STREPTOCOCCUS PNEUMONIAE, LISTERIA, HAEMOPHILUS INFLUENZAE, E. COLI, STREPTOCOCCUS AGALACTIAE, ENTEROVIRUS, HUMAN PARECHOVIRUS, HERPES SIMPLEX VIRUS TYPE 1 AND 2, HUMAN HERPESVIRUS 6, CYTOMEGALOVIRUS, VARICELLA ZOSTER VIRUS, CRYPTOCOCCUS), INCLUDES MULTIPLEX REVERSE TRANSCRIPTION, WHEN PERFORMED, AND MULTIPLEX AMPLIFIED PROBE TECHNIQUE, MULTIPLE TYPES OR SUBTYPES, 12-25 TARGETS
Source: CMS coverage guidance
CPT 0595Uhigh
INFECTIOUS DISEASE (TROPICAL FEVER PATHOGENS), VECTOR-BORNE AND ZOONOTIC PATHOGENS, INCLUDING 2 VIRUSES (CHIKUNGUNYA VIRUS AND DENGUE VIRUS SEROTYPES 1, 2, 3, AND 4), 1 BACTERIUM (LEPTOSPIRA SPECIES), AND 1 PARASITE WITH SPECIES DIFFERENTIATION (PLASMODIUM SPECIES, PLASMODIUM FALCIPARUM, AND PLASMODIUM VIVAX/OVALE), REAL-TIME RT-PCR, WHOLE BLOOD, EACH PATHOGEN REPORTED AS DETECTED OR NOT DETECTED
Source: CMS coverage guidance
CPT 87999high
UNLISTED MICROBIOLOGY PROCEDURE
Source: CMS coverage guidance
CPT 70460high
COMPUTED TOMOGRAPHY, HEAD OR BRAIN; WITH CONTRAST MATERIAL(S)
Source: CMS coverage guidance
CPT 70450high
COMPUTED TOMOGRAPHY, HEAD OR BRAIN; WITHOUT CONTRAST MATERIAL
Source: CMS coverage guidance
CPT 70470high
COMPUTED TOMOGRAPHY, HEAD OR BRAIN; WITHOUT CONTRAST MATERIAL, FOLLOWED BY CONTRAST MATERIAL(S) AND FURTHER SECTIONS
Source: CMS coverage guidance

Coding guidelines

Compatibility

Legacy and official ICD code match exactly.
Legacy codes
A86

Common synonyms

Unspecified viral encephalitis

Frequently asked questions

Code details

CodeA86
SystemICD10
Display nameUnspecified viral encephalitis
ChapterCertain infectious and parasitic diseases (A00-B99)
BlockViral and prion infections of the central nervous system

Flags

BillableYes
Valid clinical useYes

Source

SourceICD-10
Version2026-annual
Releaseannual
Year2026

Index terms

Matched terms
Encephalitis(chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Encephalitis(chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Encephalitis(chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Encephalitis(chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Encephalitis(chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Encephalitis(chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)MeningoencephalitisMeningoencephalitisMeningoencephalitisMeningoencephalomyelitis
See also
Encephalitis, viral

About this content

This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.

ICD-10 Code A86 for Unspecified viral encephalitis | HealthAssure