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
  • A54.0|

    Gonococcal infection of lower genitourinary tract without periurethral or accessory gland abscess

  • A54.00|

    Gonococcal infection of lower genitourinary tract, unspecified

  • A54.01|

    Gonococcal cystitis and urethritis, unspecified

  • A54.02|

    Gonococcal vulvovaginitis, unspecified

  • A54.03|

    Gonococcal cervicitis, unspecified

  • A54.09|

    Other gonococcal infection of lower genitourinary tract

  • A54.1|

    Gonococcal infection of lower genitourinary tract with periurethral and accessory gland abscess

  • A54.2|

    Gonococcal pelviperitonitis and other gonococcal genitourinary infection

  • A54.21|

    Gonococcal infection of kidney and ureter

  • A54.22|

    Gonococcal prostatitis

  • A54.23|

    Gonococcal infection of other male genital organs

  • A54.24|

    Gonococcal female pelvic inflammatory disease

  • A54.29|

    Other gonococcal genitourinary infections

  • A54.3|

    Gonococcal infection of eye

  • A54.30|

    Gonococcal infection of eye, unspecified

  • A54.31|

    Gonococcal conjunctivitis

  • A54.32|

    Gonococcal iridocyclitis

  • A54.33|

    Gonococcal keratitis

  • A54.39|

    Other gonococcal eye infection

  • A54.4|

    Gonococcal infection of musculoskeletal system

  • A54.40|

    Gonococcal infection of musculoskeletal system, unspecified

  • A54.41|

    Gonococcal spondylopathy

  • A54.42|

    Gonococcal arthritis

  • A54.43|

    Gonococcal osteomyelitis

  • A54.49|

    Gonococcal infection of other musculoskeletal tissue

  • A54.5|

    Gonococcal pharyngitis

  • A54.6|

    Gonococcal infection of anus and rectum

  • A54.8|

    Other gonococcal infections

  • A54.81|

    Gonococcal meningitis

  • A54.82|

    Gonococcal brain abscess

  • A54.83|

    Gonococcal heart infection

  • A54.84|

    Gonococcal pneumonia

  • A54.85|

    Gonococcal peritonitis

  • A54.86|

    Gonococcal sepsis

  • A54.89|

    Other gonococcal infections

  • A54.9|

    Gonococcal infection, unspecified

  • A55|

    Chlamydial lymphogranuloma (venereum)

  • A56|

    Other sexually transmitted chlamydial diseases

  • A56.0|

    Chlamydial infection of lower genitourinary tract

  • A56.00|

    Chlamydial infection of lower genitourinary tract, unspecified

  • A56.01|

    Chlamydial cystitis and urethritis

  • A56.02|

    Chlamydial vulvovaginitis

  • A56.09|

    Other chlamydial infection of lower genitourinary tract

  • A56.1|

    Chlamydial infection of pelviperitoneum and other genitourinary organs

  • A56.11|

    Chlamydial female pelvic inflammatory disease

  • A56.19|

    Other chlamydial genitourinary infection

  • A56.2|

    Chlamydial infection of genitourinary tract, unspecified

  • A56.3|

    Chlamydial infection of anus and rectum

  • A56.4|

    Chlamydial infection of pharynx

  • A56.8|

    Sexually transmitted chlamydial infection of other sites

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