Chapter 1

A00–B99: Certain Infectious and Parasitic Diseases

Certain Infectious and Parasitic Diseases diagnostic classification updated for 2026.

Chapter Instructions

Includes
  • diseases generally recognized as communicable or transmissible
Excludes1(Not coded here. Use a different code.)
  • certain localized infections - see body system-related chapters
Excludes2(Not included here. Code separately if applicable.)
  • 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
  • code to identify resistance to antimicrobial drugs (Z16.-)
Internal Codes
  • A81.09

    Other Creutzfeldt-Jakob disease

  • A81.1

    Subacute sclerosing panencephalitis

  • A81.2

    Progressive multifocal leukoencephalopathy

  • A81.81

    Kuru

  • 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

  • A82.0

    Sylvatic rabies

  • A82.1

    Urban rabies

  • A82.9

    Rabies, unspecified

  • 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

  • A84.0

    Far Eastern tick-borne encephalitis [Russian spring-summer encephalitis]

  • A84.1

    Central European tick-borne encephalitis

  • A84.81

    Powassan virus disease

  • A84.89

    Other tick-borne viral encephalitis

  • A84.9

    Tick-borne viral encephalitis, unspecified

  • A85.0

    Enteroviral encephalitis

  • A85.1

    Adenoviral encephalitis

  • A85.2

    Arthropod-borne viral encephalitis, unspecified

  • A85.8

    Other specified viral encephalitis

  • A86

    Unspecified viral encephalitis

  • A87.0

    Enteroviral meningitis

  • A87.1

    Adenoviral meningitis

  • A87.2

    Lymphocytic choriomeningitis

  • A87.8

    Other viral meningitis

  • A87.9

    Viral meningitis, unspecified

  • A88.0

    Enteroviral exanthematous fever [Boston exanthem]

  • A88.1

    Epidemic vertigo

  • A88.8

    Other specified viral infections of central nervous system

  • A89

    Unspecified viral infection of central nervous system

  • A90

    Dengue fever [classical dengue]

  • A91

    Dengue hemorrhagic fever

  • A92.0

    Chikungunya virus disease

  • A92.1

    O'nyong-nyong fever

  • A92.2

    Venezuelan equine fever

  • A92.30

    West Nile virus infection, unspecified

  • A92.31

    West Nile virus infection with encephalitis

  • A92.32

    West Nile virus infection with other neurologic manifestation

  • A92.39

    West Nile virus infection with other complications

  • A92.4

    Rift Valley fever

  • A92.5

    Zika virus disease

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