DxCodebookFY2027 · Oct 1, 2026 – Sep 30, 2027

Category · FY2027

A84 Tick-borne viral encephalitis

  • Header · not billable

A84 is not billable. The category heads 5 billable codes in FY2027, grouped under 4 subdivisions.

Index → code

  • Louping ill (encephalitis) → A84.89
  • Russian spring-summer type encephalitis → A84.0
  • Meningoencephalitisdiphasic → A84.1

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. A84 Tick-borne viral encephalitis
Billable codes
5
Subdivisions
4
CC / MCC codes
0 / 5
HCC V28 codes
0
New FY2027
0
Index entries
21

Codes in A84

  1. A84.0
    Far Eastern tick-borne encephalitis [Russian spring-summer encephalitis]
    BillableMCC
  2. A84.1
    Central European tick-borne encephalitis
    BillableMCC
  3. A84.8
    Other tick-borne viral encephalitis
    Header
  4. A84.81
    Powassan virus disease
    BillableMCC
  5. A84.89
    Other tick-borne viral encephalitis
    BillableMCC
    Inclusion terms 1, Code first 1

    Inclusion terms

    • Louping ill

    Code first

    • , if applicable, transfusion related infection (T80.22-) T80.22
  6. A84.9
    Tick-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 A84

Includes

  • tick-borne viral meningoencephalitis

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

  • Russian spring-summer type encephalitis → A84.0
  • Louping ill (encephalitis) → A84.89
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Far Eastern (tick-borne) → A84.0
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Central European (tick-borne) → A84.1
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Czechoslovakian → A84.1
  • Meningoencephalitisdiphasic → A84.1
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Powassan → A84.81
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)louping ill → A84.89
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)tick-borne → A84.9
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)Russianspring-summer (taiga) → A84.0
  • Disease, diseasedviral, virusPowassan → A84.81
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virustick-borne, specified NEC → A84.89
  • Infection, infected, infective (opportunistic)virus, viral NOSencephalitis, tick-borne → A84.9
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECtick-borne → A84.9
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECtick-borneFar Eastern → A84.0
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECtick-borneRussian spring-summer (taiga) → A84.0
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECtick-bornebiundulant → A84.1
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECtick-bornecentral European → A84.1
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECtick-borneCzechoslovakian → A84.1
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECtick-bornediphasic meningoencephalitis → A84.1
  • Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)viral, virusarthropod-borne NECtick-bornespecified NEC → A84.89

NCHS Alphabetic Index. Index first, then the Tabular List.

Hierarchy