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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B00.4|
Herpesviral encephalitis
B00.5|
Herpesviral ocular disease
B00.50|
Herpesviral ocular disease, unspecified
B00.51|
Herpesviral iridocyclitis
B00.52|
Herpesviral keratitis
B00.53|
Herpesviral conjunctivitis
B00.59|
Other herpesviral disease of eye
B00.7|
Disseminated herpesviral disease
B00.8|
Other forms of herpesviral infections
B00.81|
Herpesviral hepatitis
B00.82|
Herpes simplex myelitis
B00.89|
Other herpesviral infection
B00.9|
Herpesviral infection, unspecified
B01|
Varicella [chickenpox]
B01.0|
Varicella meningitis
B01.1|
Varicella encephalitis, myelitis and encephalomyelitis
B01.11|
Varicella encephalitis and encephalomyelitis
B01.12|
Varicella myelitis
B01.2|
Varicella pneumonia
B01.8|
Varicella with other complications
B01.81|
Varicella keratitis
B01.89|
Other varicella complications
B01.9|
Varicella without complication
B02|
Zoster [herpes zoster]
B02.0|
Zoster encephalitis
B02.1|
Zoster meningitis
B02.2|
Zoster with other nervous system involvement
B02.21|
Postherpetic geniculate ganglionitis
B02.22|
Postherpetic trigeminal neuralgia
B02.23|
Postherpetic polyneuropathy
B02.24|
Postherpetic myelitis
B02.29|
Other postherpetic nervous system involvement
B02.3|
Zoster ocular disease
B02.30|
Zoster ocular disease, unspecified
B02.31|
Zoster conjunctivitis
B02.32|
Zoster iridocyclitis
B02.33|
Zoster keratitis
B02.34|
Zoster scleritis
B02.39|
Other herpes zoster eye disease
B02.7|
Disseminated zoster
B02.8|
Zoster with other complications
B02.9|
Zoster without complications
B03|
Smallpox
B04|
Monkeypox
B05|
Measles
B05.0|
Measles complicated by encephalitis
B05.1|
Measles complicated by meningitis
B05.2|
Measles complicated by pneumonia
B05.3|
Measles complicated by otitis media
B05.4|
Measles with intestinal complications

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