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.-)

All Codes Billable Only

Internal Codes

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A49.02|
Methicillin resistant Staphylococcus aureus infection, unspecified site
A49.1|
Streptococcal infection, unspecified site
A49.2|
Hemophilus influenzae infection, unspecified site
A49.3|
Mycoplasma infection, unspecified site
A49.8|
Other bacterial infections of unspecified site
A49.9|
Bacterial infection, unspecified
A50|
Congenital syphilis
A50.0|
Early congenital syphilis, symptomatic
A50.01|
Early congenital syphilitic oculopathy
A50.02|
Early congenital syphilitic osteochondropathy
A50.03|
Early congenital syphilitic pharyngitis
A50.04|
Early congenital syphilitic pneumonia
A50.05|
Early congenital syphilitic rhinitis
A50.06|
Early cutaneous congenital syphilis
A50.07|
Early mucocutaneous congenital syphilis
A50.08|
Early visceral congenital syphilis
A50.09|
Other early congenital syphilis, symptomatic
A50.1|
Early congenital syphilis, latent
A50.2|
Early congenital syphilis, unspecified
A50.3|
Late congenital syphilitic oculopathy
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
A50.4|
Late congenital neurosyphilis [juvenile neurosyphilis]
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
A50.5|
Other late congenital syphilis, symptomatic
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|
Early syphilis
A51.0|
Primary genital syphilis
A51.1|
Primary anal syphilis
A51.2|
Primary syphilis of other sites
A51.3|
Secondary syphilis of skin and mucous membranes
A51.31|
Condyloma latum

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