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    v1.0.28
    OpenPayerBilling CodesViral and prion infections of the central nervous systemICD-10-CM a84-tick-borne-viral-encephalitis
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    ICD-10-CM Code For Tick-Borne Viral Encephalitis: Group Overview

    The International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) code group A84 includes tick-borne viral encephalitis diagnoses such as infections caused by tick-borne encephalitis viruses affecting the brain and associated central nervous system structures. These ICD-10-CM diagnosis codes are used to document clinical presentations ranging from meningitis to encephalitis and meningoencephalitis, capturing disease severity, neurologic involvement, and complications. Accurate coding within the ICD-10-CM A84 group supports proper claim adjudication, complete clinical documentation, and appropriate reimbursement.

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    ICD-10-CM A84: Tick-borne Viral Encephalitis Overview

    The diagnoses in this group represent tick-borne viral infections that primarily involve the central nervous system, including encephalitis caused by tick-transmitted viruses. These conditions target the brain and meninges and can present with neurologic deficits, altered mental status, or meningoencephalitis. Accurate coding ensures clinical severity and organ involvement are documented, which is important for correct claim processing and reimbursement.

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    When to Use

    Use a code from this group when a patient has a confirmed or strongly suspected tick-borne viral infection involving the brain or meninges documented by clinical evaluation or laboratory testing. Select the code that best reflects the clinical presentation and any neurologic complications to accurately represent the encounter.

    ICD-10-CM Codes

    5 rows

    ICD-10-CM CodeDescription
    A84.0Far Eastern tick-borne encephalitis [Russian spring-summer encephalitis]
    A84.1Central European tick-borne encephalitis
    A84.81Powassan virus disease
    A84.89Other tick-borne viral encephalitis
    A84.9Tick-borne viral encephalitis, unspecified

    DRG Codes

    5 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

    Typical Clinical Scenarios

    • An adult hiker presents to the emergency department with sudden onset high fever, severe headache, confusion, and neck stiffness two days after a tick bite in an endemic area. Neurologic examination shows altered mental status and photophobia; lumbar puncture reveals lymphocytic pleocytosis and viral PCR confirms a tick-borne flaviviral etiology, prompting acute inpatient management and assignment of A84.0. Typical codes: A84.0
    • An elderly patient with a recent diagnosis of tick-borne encephalitis is seen in the neurology clinic several weeks after hospital discharge for persistent cognitive deficits, gait instability, and fatigue impacting activities of daily living. This visit documents ongoing neurologic sequelae attributed to the prior viral central nervous system infection, and a post-encephalitic or persistent condition code from the group is used to capture the continuing care needs. Typical codes: A84.1, A84.9
    • A hospitalized immunocompromised patient develops altered consciousness and focal seizures after known tick exposure; imaging shows multifocal cerebral inflammation and microbiologic testing does not identify bacterial causes. Because the encephalitic syndrome is due to a tick-borne viral agent and represents a serious comorbidity complicating the hospital course, an acute viral encephalitis code from the group is assigned to reflect the infectious neurologic complication. Typical codes: A84.0, A84.89

    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

    A85-OTHER-VIRAL-ENCEPHALITIS

    ICD-10-CM Code For Other Viral Encephalitis Not Elsewhere Classified: 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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