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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A80.30|
Acute paralytic poliomyelitis, unspecified
A80.39|
Other acute paralytic poliomyelitis
A80.4|
Acute nonparalytic poliomyelitis
A80.9|
Acute poliomyelitis, unspecified
A81|
Atypical virus infections of central nervous system
A81.0|
Creutzfeldt-Jakob disease
A81.00|
Creutzfeldt-Jakob disease, unspecified
A81.01|
Variant Creutzfeldt-Jakob disease
A81.09|
Other Creutzfeldt-Jakob disease
A81.1|
Subacute sclerosing panencephalitis
A81.2|
Progressive multifocal leukoencephalopathy
A81.8|
Other atypical virus infections of central nervous system
A81.81|
Kuru
A81.82|
Gerstmann-Sträussler-Scheinker syndrome
A81.83|
Fatal familial insomnia
A81.89|
Other atypical virus infections of central nervous system
A81.9|
Atypical virus infection of central nervous system, unspecified
A82|
Rabies
A82.0|
Sylvatic rabies
A82.1|
Urban rabies
A82.9|
Rabies, unspecified
A83|
Mosquito-borne viral encephalitis
A83.0|
Japanese encephalitis
A83.1|
Western equine encephalitis
A83.2|
Eastern equine encephalitis
A83.3|
St Louis encephalitis
A83.4|
Australian encephalitis
A83.5|
California encephalitis
A83.6|
Rocio virus disease
A83.8|
Other mosquito-borne viral encephalitis
A83.9|
Mosquito-borne viral encephalitis, unspecified
A84|
Tick-borne viral encephalitis
A84.0|
Far Eastern tick-borne encephalitis [Russian spring-summer encephalitis]
A84.1|
Central European tick-borne encephalitis
A84.8|
Other tick-borne viral encephalitis
A84.81|
Powassan virus disease
A84.89|
Other tick-borne viral encephalitis
A84.9|
Tick-borne viral encephalitis, unspecified
A85|
Other viral encephalitis, not elsewhere classified
A85.0|
Enteroviral encephalitis
A85.1|
Adenoviral encephalitis
A85.2|
Arthropod-borne viral encephalitis, unspecified
A85.8|
Other specified viral encephalitis
A86|
Unspecified viral encephalitis
A87|
Viral meningitis
A87.0|
Enteroviral meningitis
A87.1|
Adenoviral meningitis
A87.2|
Lymphocytic choriomeningitis
A87.8|
Other viral meningitis
A87.9|
Viral meningitis, unspecified

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