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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A69.2|
Lyme disease
A69.20|
Lyme disease, unspecified
A69.21|
Meningitis due to Lyme disease
A69.22|
Other neurologic disorders in Lyme disease
A69.23|
Arthritis due to Lyme disease
A69.29|
Other conditions associated with Lyme disease
A69.8|
Other specified spirochetal infections
A69.9|
Spirochetal infection, unspecified
A70|
Chlamydia psittaci infections
A71|
Trachoma
A71.0|
Initial stage of trachoma
A71.1|
Active stage of trachoma
A71.9|
Trachoma, unspecified
A74|
Other diseases caused by chlamydiae
A74.0|
Chlamydial conjunctivitis
A74.8|
Other chlamydial diseases
A74.81|
Chlamydial peritonitis
A74.89|
Other chlamydial diseases
A74.9|
Chlamydial infection, unspecified
A75|
Typhus fever
A75.0|
Epidemic louse-borne typhus fever due to Rickettsia prowazekii
A75.1|
Recrudescent typhus [Brill's disease]
A75.2|
Typhus fever due to Rickettsia typhi
A75.3|
Typhus fever due to Rickettsia tsutsugamushi
A75.9|
Typhus fever, unspecified
A77|
Spotted fever [tick-borne rickettsioses]
A77.0|
Spotted fever due to Rickettsia rickettsii
A77.1|
Spotted fever due to Rickettsia conorii
A77.2|
Spotted fever due to Rickettsia siberica
A77.3|
Spotted fever due to Rickettsia australis
A77.4|
Ehrlichiosis
A77.40|
Ehrlichiosis, unspecified
A77.41|
Ehrlichiosis chaffeensis [E. chaffeensis]
A77.49|
Other ehrlichiosis
A77.8|
Other spotted fevers
A77.9|
Spotted fever, unspecified
A78|
Q fever
A79|
Other rickettsioses
A79.0|
Trench fever
A79.1|
Rickettsialpox due to Rickettsia akari
A79.8|
Other specified rickettsioses
A79.81|
Rickettsiosis due to Ehrlichia sennetsu
A79.82|
Anaplasmosis [A. phagocytophilum]
A79.89|
Other specified rickettsioses
A79.9|
Rickettsiosis, unspecified
A80|
Acute poliomyelitis
A80.0|
Acute paralytic poliomyelitis, vaccine-associated
A80.1|
Acute paralytic poliomyelitis, wild virus, imported
A80.2|
Acute paralytic poliomyelitis, wild virus, indigenous
A80.3|
Acute paralytic poliomyelitis, other and unspecified

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