2020 ICD-10-CM Diagnosis Code A83.1

Western equine encephalitis

    2016 2017 2018 2019 2020 Billable/Specific Code
  • A83.1 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.
  • The 2020 edition of ICD-10-CM A83.1 became effective on October 1, 2019.
  • This is the American ICD-10-CM version of A83.1 - other international versions of ICD-10 A83.1 may differ.
The following code(s) above A83.1 contain annotation back-references
Annotation Back-References
In this context, annotation back-references refer to codes that contain:
  • Applicable To annotations, or
  • Code Also annotations, or
  • Code First annotations, or
  • Excludes1 annotations, or
  • Excludes2 annotations, or
  • Includes annotations, or
  • Note annotations, or
  • Use Additional annotations
that may be applicable to A83.1:
  • A00-B99
    2020 ICD-10-CM Range A00-B99

    Certain infectious and parasitic diseases

    Includes
    • diseases generally recognized as communicable or transmissible
    Type 1 Excludes
    • certain localized infections - see body system-related chapters
    Type 2 Excludes
    • carrier or suspected carrier of infectious disease (Z22.-)
    • infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
    • infectious and parasitic diseases specific to the perinatal period (P35-P39)
    • influenza and other acute respiratory infections (J00-J22)
    Use Additional
    • code to identify resistance to antimicrobial drugs (Z16.-)
    Certain infectious and parasitic diseases
  • A80-A89
    2020 ICD-10-CM Range A80-A89

    Viral and prion infections of the central nervous system

    Type 1 Excludes
    • postpolio syndrome (G14)
    • sequelae of poliomyelitis (B91)
    • sequelae of viral encephalitis (B94.1)
    Viral and prion infections of the central nervous system
  • A83
    ICD-10-CM Diagnosis Code A83

    Mosquito-borne viral encephalitis

      2016 2017 2018 2019 2020 Non-Billable/Non-Specific Code
    Includes
    • mosquito-borne viral meningoencephalitis
    Type 2 Excludes
    • Venezuelan equine encephalitis (A92.2)
    • West Nile fever (A92.3-)
    • West Nile virus (A92.3-)
    Mosquito-borne viral encephalitis
Clinical Information
  • A form of arboviral encephalitis (which primarily affects horses) endemic to western and central regions of north america. The causative organism (encephalomyelitis virus, western equine) may be transferred to humans via the bite of mosquitoes (culex tarsalis and others). Clinical manifestations include headache and influenza-like symptoms followed by alterations in mentation, seizures, and coma. Death occurs in a minority of cases. Survivors may recover fully or be left with residual neurologic dysfunction, including parkinsonism, postencephalitic. (from Joynt, Clinical Neurology, 1996, ch26, pp8-9)
  • A mosquito-born viral infection caused by the western equine encephalitis virus. The signs and symptoms range from flu-like illness to permanent central nervous system damage, coma, and death.
  • Form of arboviral encephalitis which primarily affects horses, endemic to western and central north america; the virus may be transferred to humans via mosquito bite; clinical manifestations include headache and influenza-like symptoms followed by alterations in mentation, seizures and coma; survivors may be left with residual neurologic dysfunction.
ICD-10-CM A83.1 is grouped within Diagnostic Related Group(s) (MS-DRG v37.0):
  • 023 Craniotomy with major device implant or acute complex cns pdx with mcc or chemotherapy implant or epilepsy with neurostimulator
  • 024 Craniotomy with major device implant or acute complex cns pdx without mcc
  • 097 Non-bacterial infection of nervous system except viral meningitis with mcc
  • 098 Non-bacterial infection of nervous system except viral meningitis with cc
  • 099 Non-bacterial infection of nervous system except viral meningitis without cc/mcc

Convert A83.1 to ICD-9-CM

Code History
  • 2016 (effective 10/1/2015): New code (first year of non-draft ICD-10-CM)
  • 2017 (effective 10/1/2016): No change
  • 2018 (effective 10/1/2017): No change
  • 2019 (effective 10/1/2018): No change
  • 2020 (effective 10/1/2019): No change

Diagnosis Index entries containing back-references to A83.1:
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute) G04.90
    ICD-10-CM Diagnosis Code G04.90

    Encephalitis and encephalomyelitis, unspecified

      2016 2017 2018 2019 2020 Billable/Specific Code
    Applicable To
    • Ventriculitis (cerebral) NOS
    • equine (acute) (infectious) (viral) A83.9
      ICD-10-CM Diagnosis Code A83.9

      Mosquito-borne viral encephalitis, unspecified

        2016 2017 2018 2019 2020 Billable/Specific Code
      • Western A83.1
    • viral, virus A86
      ICD-10-CM Diagnosis Code A86

      Unspecified viral encephalitis

        2016 2017 2018 2019 2020 Billable/Specific Code
      Applicable To
      • Viral encephalomyelitis NOS
      • Viral meningoencephalitis NOS
      • arthropod-borne NEC A85.2
        ICD-10-CM Diagnosis Code A85.2

        Arthropod-borne viral encephalitis, unspecified

          2016 2017 2018 2019 2020 Billable/Specific Code
        Type 1 Excludes
        • West nile virus with encephalitis (A92.31)
        • mosquito-borne A83.9
          ICD-10-CM Diagnosis Code A83.9

          Mosquito-borne viral encephalitis, unspecified

            2016 2017 2018 2019 2020 Billable/Specific Code
          • Western equine A83.1
    • Western equine A83.1
  • Encephalomyelitis G04.90
    - see also Encephalitis
    ICD-10-CM Diagnosis Code G04.90

    Encephalitis and encephalomyelitis, unspecified

      2016 2017 2018 2019 2020 Billable/Specific Code
    Applicable To
    • Ventriculitis (cerebral) NOS
    • equine A83.9
      ICD-10-CM Diagnosis Code A83.9

      Mosquito-borne viral encephalitis, unspecified

        2016 2017 2018 2019 2020 Billable/Specific Code
      • Western A83.1

ICD-10-CM Codes Adjacent To A83.1
A81.82 Gerstmann-Sträussler-Scheinker syndrome
A81.83 Fatal familial insomnia
A81.89 Other atypical virus infections of central nervous system
A81.9 Atypical virus infection of central nervous system, unspecified
A82 Rabies
A82.0 Sylvatic rabies
A82.1 Urban rabies
A82.9 Rabies, unspecified
A83 Mosquito-borne viral encephalitis
A83.0 Japanese encephalitis
A83.1 Western equine encephalitis
A83.2 Eastern equine encephalitis
A83.3 St Louis encephalitis
A83.4 Australian encephalitis
A83.5 California encephalitis
A83.6 Rocio virus disease
A83.8 Other mosquito-borne viral encephalitis
A83.9 Mosquito-borne viral encephalitis, unspecified
A84 Tick-borne viral encephalitis
A84.0 Far Eastern tick-borne encephalitis [Russian spring-summer encephalitis]
A84.1 Central European tick-borne encephalitis

Reimbursement claims with a date of service on or after October 1, 2015 require the use of ICD-10-CM codes.