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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A27|
Leptospirosis
A27.0|
Leptospirosis icterohemorrhagica
A27.8|
Other forms of leptospirosis
A27.81|
Aseptic meningitis in leptospirosis
A27.89|
Other forms of leptospirosis
A27.9|
Leptospirosis, unspecified
A28|
Other zoonotic bacterial diseases, not elsewhere classified
A28.0|
Pasteurellosis
A28.1|
Cat-scratch disease
A28.2|
Extraintestinal yersiniosis
A28.8|
Other specified zoonotic bacterial diseases, not elsewhere classified
A28.9|
Zoonotic bacterial disease, unspecified
A30|
Leprosy [Hansen's disease]
A30.0|
Indeterminate leprosy
A30.1|
Tuberculoid leprosy
A30.2|
Borderline tuberculoid leprosy
A30.3|
Borderline leprosy
A30.4|
Borderline lepromatous leprosy
A30.5|
Lepromatous leprosy
A30.8|
Other forms of leprosy
A30.9|
Leprosy, unspecified
A31|
Infection due to other mycobacteria
A31.0|
Pulmonary mycobacterial infection
A31.1|
Cutaneous mycobacterial infection
A31.2|
Disseminated mycobacterium avium-intracellulare complex (DMAC)
A31.8|
Other mycobacterial infections
A31.9|
Mycobacterial infection, unspecified
A32|
Listeriosis
A32.0|
Cutaneous listeriosis
A32.1|
Listerial meningitis and meningoencephalitis
A32.11|
Listerial meningitis
A32.12|
Listerial meningoencephalitis
A32.7|
Listerial sepsis
A32.8|
Other forms of listeriosis
A32.81|
Oculoglandular listeriosis
A32.82|
Listerial endocarditis
A32.89|
Other forms of listeriosis
A32.9|
Listeriosis, unspecified
A33|
Tetanus neonatorum
A34|
Obstetrical tetanus
A35|
Other tetanus
A36|
Diphtheria
A36.0|
Pharyngeal diphtheria
A36.1|
Nasopharyngeal diphtheria
A36.2|
Laryngeal diphtheria
A36.3|
Cutaneous diphtheria
A36.8|
Other diphtheria
A36.81|
Diphtheritic cardiomyopathy
A36.82|
Diphtheritic radiculomyelitis
A36.83|
Diphtheritic polyneuritis

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