DxCodebookFY2027 · Oct 1, 2026 – Sep 30, 2027

Category · FY2027

A83 Mosquito-borne viral encephalitis

  • Header · not billable

A83 is not billable. The category heads 9 billable codes in FY2027: the 9 codes directly below it.

Index → code

  • Borna disease → A83.9
  • Arboencephalitis, Australian → A83.4
  • AustralianX disease → A83.4

Where it sits

  1. Chapter 1 Certain infectious and parasitic diseases (A00-B99)
  2. A80-A89 Viral and prion infections of the central nervous system (A80-A89)
  3. A83 Mosquito-borne viral encephalitis
Billable codes
9
Subdivisions
9
CC / MCC codes
0 / 9
HCC V28 codes
0
New FY2027
0
Index entries
41

Codes in A83

  1. A83.0
    Japanese encephalitis
    BillableMCC
  2. A83.1
    Western equine encephalitis
    BillableMCC
  3. A83.2
    Eastern equine encephalitis
    BillableMCC
  4. A83.3
    St Louis encephalitis
    BillableMCC
  5. A83.4
    Australian encephalitis
    BillableMCC
    Inclusion terms 1

    Inclusion terms

    • Kunjin virus disease
  6. A83.5
    California encephalitis
    BillableMCC
    Inclusion terms 2

    Inclusion terms

    • California meningoencephalitis
    • La Crosse encephalitis
  7. A83.6
    Rocio virus disease
    BillableMCC
  8. A83.8
    Other mosquito-borne viral encephalitis
    BillableMCC
  9. A83.9
    Mosquito-borne viral encephalitis, unspecified
    BillableMCC

CC/MCC: as a secondary diagnosis, unless the principal diagnosis is on the code’s PDX exclusion list (MS-DRG v44 Appendix C; list on the code card).

Sources of each column.

Instructions

At A83

Includes

  • mosquito-borne viral meningoencephalitis

Excludes2

  • Venezuelan equine encephalitis (A92.2) A92.2
  • West Nile fever (A92.3-) A92.3
  • West Nile virus (A92.3-) A92.3

Notes that also apply

Block A80-A89 instructions (Excludes1 3): printed on the block page.

Chapter 1 instructions (Includes 1, Excludes2 5, Use additional code 1): printed on the chapter 1 page.

Index entries

  • Arboencephalitis, Australian → A83.4
  • Borna disease → A83.9
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Japanese (B type) → A83.0
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)summer → A83.0
  • Infection, infected, infective (opportunistic)Japanese B encephalitis → A83.0
  • JapaneseB-type encephalitis → A83.0
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Western equine → A83.1
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Eastern equine → A83.2
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)St. Louis → A83.3
  • AustralianX disease → A83.4
  • Disease, diseasedAustralian X → A83.4
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Australian → A83.4
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Murray Valley → A83.4
  • Californiaencephalitis → A83.5
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)California (virus) → A83.5
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)La Crosse → A83.5
  • MeningoencephalitisCalifornia → A83.5
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Ilheus (virus) → A83.8
  • Disease, diseasedBorna → A83.9
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)equine (acute) (infectious) (viral) → A83.9
  • Encephalomyelitisequine → A83.9
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Russianautumnal → A83.0
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)typeB → A83.0
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)equine (acute) (infectious) (viral)Western → A83.1
  • EncephalomyelitisequineWestern → A83.1
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)equine (acute) (infectious) (viral)Eastern → A83.2
  • EncephalomyelitisequineEastern → A83.2
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)typeC → A83.3
  • Disease, diseasedviral, virusKunjin → A83.4
  • Disease, diseasedviral, virusRocio (encephalitis) → A83.6
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECmosquito-borne → A83.9
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECmosquito-borneJapanese (B type) → A83.0
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECmosquito-bornetype B → A83.0
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECmosquito-borneWestern equine → A83.1
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECmosquito-borneEastern equine → A83.2
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECmosquito-borneSt. Louis → A83.3
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECmosquito-bornetype C → A83.3
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECmosquito-borneAustralian X disease → A83.4
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECmosquito-borneMurray Valley → A83.4
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECmosquito-borneCalifornia virus → A83.5

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