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
  • A50.09

    Other early congenital syphilis, symptomatic

  • A50.1

    Early congenital syphilis, latent

  • A50.2

    Early congenital syphilis, unspecified

  • A50.30

    Late congenital syphilitic oculopathy, unspecified

  • A50.31

    Late congenital syphilitic interstitial keratitis

  • A50.32

    Late congenital syphilitic chorioretinitis

  • A50.39

    Other late congenital syphilitic oculopathy

  • A50.40

    Late congenital neurosyphilis, unspecified

  • A50.41

    Late congenital syphilitic meningitis

  • A50.42

    Late congenital syphilitic encephalitis

  • A50.43

    Late congenital syphilitic polyneuropathy

  • A50.44

    Late congenital syphilitic optic nerve atrophy

  • A50.45

    Juvenile general paresis

  • A50.49

    Other late congenital neurosyphilis

  • A50.51

    Clutton's joints

  • A50.52

    Hutchinson's teeth

  • A50.53

    Hutchinson's triad

  • A50.54

    Late congenital cardiovascular syphilis

  • A50.55

    Late congenital syphilitic arthropathy

  • A50.56

    Late congenital syphilitic osteochondropathy

  • A50.57

    Syphilitic saddle nose

  • A50.59

    Other late congenital syphilis, symptomatic

  • A50.6

    Late congenital syphilis, latent

  • A50.7

    Late congenital syphilis, unspecified

  • A50.9

    Congenital syphilis, unspecified

  • A51.0

    Primary genital syphilis

  • A51.1

    Primary anal syphilis

  • A51.2

    Primary syphilis of other sites

  • A51.31

    Condyloma latum

  • A51.32

    Syphilitic alopecia

  • A51.39

    Other secondary syphilis of skin

  • A51.41

    Secondary syphilitic meningitis

  • A51.42

    Secondary syphilitic female pelvic disease

  • A51.43

    Secondary syphilitic oculopathy

  • A51.44

    Secondary syphilitic nephritis

  • A51.45

    Secondary syphilitic hepatitis

  • A51.46

    Secondary syphilitic osteopathy

  • A51.49

    Other secondary syphilitic conditions

  • A51.5

    Early syphilis, latent

  • A51.9

    Early syphilis, unspecified

  • A52.00

    Cardiovascular syphilis, unspecified

  • A52.01

    Syphilitic aneurysm of aorta

  • A52.02

    Syphilitic aortitis

  • A52.03

    Syphilitic endocarditis

  • A52.04

    Syphilitic cerebral arteritis

  • A52.05

    Other cerebrovascular syphilis

  • A52.06

    Other syphilitic heart involvement

  • A52.09

    Other cardiovascular syphilis

  • A52.10

    Symptomatic neurosyphilis, unspecified

  • A52.11

    Tabes dorsalis

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