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    v1.0.28
    OpenPayerBilling CodesViral and prion infections of the central nervous systemICD-10-CM a85-other-viral-encephalitis
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    ICD-10-CM Code For Other Viral Encephalitis Not Elsewhere Classified: Group Overview

    The International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) code group A85 includes viral encephalitis cases that are not classified under more specific viral encephalitis codes, encompassing unspecified viral causes and uncommon viral agents affecting the brain. These ICD-10-CM diagnosis codes are used to document acute inflammatory brain infections where the viral etiology is unspecified, rare, or otherwise not captured by more specific codes, capturing disease severity and central nervous system involvement. Accurate coding within the ICD-10-CM A85 group supports proper claim adjudication and complete clinical documentation for appropriate reimbursement.

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    ICD-10-CM A85: Other Viral Encephalitis, Not Elsewhere Classified Overview

    The ICD-10-CM A85 group represents viral infections of the brain caused by viruses not assigned to more specific encephalitis codes, targeting the central nervous system. These diagnoses describe inflammatory processes of the brain parenchyma due to unspecified or rare viral etiologies. Accurate coding matters for appropriate claim adjudication and reflects clinical severity and resource use relevant to reimbursement.

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    When to Use

    Use a code from this group when a patient has clinical and diagnostic evidence of viral encephalitis but the viral agent is not identified or does not have a dedicated ICD-10-CM code. These codes apply when documentation indicates viral encephalitis of the central nervous system without specification to a more precise viral etiology.

    ICD-10-CM Codes

    4 rows

    ICD-10-CM CodeDescription
    A85.0Enteroviral encephalitis
    A85.1Adenoviral encephalitis
    A85.2Arthropod-borne viral encephalitis, unspecified
    A85.8Other specified viral encephalitis

    DRG Codes

    8 rows

    DRG CodeDescription
    023Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis with MCC or Antineoplastic Implant or Epilepsy with Neurostimulator
    024Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis without MCC
    097Non-Bacterial Infection of Nervous System Except Viral Meningitis with MCC
    098Non-Bacterial Infection of Nervous System Except Viral Meningitis with CC
    099Non-Bacterial Infection of Nervous System Except Viral Meningitis without CC/MCC
    974HIV with Major Related Condition with MCC
    975HIV with Major Related Condition with CC
    976HIV with Major Related Condition without CC/MCC

    Typical Clinical Scenarios

    • An adult patient presents to the emergency department with acute onset high fever, severe headache, confusion, and new focal neurologic deficits after several days of systemic viral prodrome; lumbar puncture shows lymphocytic pleocytosis and elevated protein, and MRI reveals inflammation consistent with viral encephalitis. Because the etiology is not identified after initial testing and no specific viral agent is confirmed, a nonspecific acute viral encephalitis code from this group is assigned to capture the acute central nervous system infection. Typical codes: A85.1
    • An elderly nursing home resident develops subacute cognitive decline, persistent lethargy, and intermittent seizures over weeks following a documented systemic viral infection; workup excludes bacterial causes and PCR testing for common neurotropic viruses is negative or inconclusive. The diagnosis reflects ongoing viral encephalitic involvement of the brain that is not otherwise classified, used for management and monitoring of the protracted central nervous system condition. Typical codes: A85.2
    • A previously healthy child is admitted with sudden high fever and rapidly progressive altered mental status; despite empiric antiviral therapy and supportive care, the clinical course is severe and complicated by respiratory failure requiring ICU care. When the specific viral cause cannot be determined but the presentation represents a severe, unspecified viral encephalitis needing intensive treatment and critical care resources, an unspecified code from this group is used to document the acute serious viral CNS infection. Typical codes: A85.0, A85.8

    Related Codes

    A80-ACUTE-POLIOMYELITIS

    ICD-10-CM Code For Acute Poliomyelitis: Group Overview

    A81-ATYPICAL-VIRUS-INFECTIONS-CENTRAL-NERVOUS-SYSTEM

    ICD-10-CM Code For Atypical Virus Infections Of Central Nervous System: Group Overview

    A82-RABIES

    ICD-10-CM Code For Rabies: Group Overview

    A83-MOSQUITO-BORNE-VIRAL-ENCEPHALITIS

    ICD-10-CM Code For Mosquito-Borne Viral Encephalitis: Group Overview

    A84-TICK-BORNE-VIRAL-ENCEPHALITIS

    ICD-10-CM Code For Tick-Borne Viral Encephalitis: Group Overview

    A86-UNSPECIFIED-VIRAL-ENCEPHALITIS

    ICD-10-CM Code For Unspecified Viral Encephalitis: Group Overview

    A87-VIRAL-MENINGITIS

    ICD-10-CM Code For Viral Meningitis: Group Overview

    A88-OTHER-VIRAL-CENTRAL-NERVOUS-SYSTEM-INFECTIONS

    ICD-10-CM Code For Other Viral Infections Of Central Nervous System Not Elsewhere Classified: Group Overview

    A89-UNSPECIFIED-VIRAL-INFECTION-CENTRAL-NERVOUS-SYSTEM

    ICD-10-CM Code For Unspecified Viral Infection Of Central Nervous System: Group Overview

    Frequently Asked Questions

    References

    1. 1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
    2. 2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
    3. 3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.
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