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

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Internal Codes

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A00|
Cholera
A00.0|
Cholera due to Vibrio cholerae 01, biovar cholerae
A00.1|
Cholera due to Vibrio cholerae 01, biovar eltor
A00.9|
Cholera, unspecified
A01|
Typhoid and paratyphoid fevers
A01.0|
Typhoid fever
A01.00|
Typhoid fever, unspecified
A01.01|
Typhoid meningitis
A01.02|
Typhoid fever with heart involvement
A01.03|
Typhoid pneumonia
A01.04|
Typhoid arthritis
A01.05|
Typhoid osteomyelitis
A01.09|
Typhoid fever with other complications
A01.1|
Paratyphoid fever A
A01.2|
Paratyphoid fever B
A01.3|
Paratyphoid fever C
A01.4|
Paratyphoid fever, unspecified
A02|
Other salmonella infections
A02.0|
Salmonella enteritis
A02.1|
Salmonella sepsis
A02.2|
Localized salmonella infections
A02.20|
Localized salmonella infection, unspecified
A02.21|
Salmonella meningitis
A02.22|
Salmonella pneumonia
A02.23|
Salmonella arthritis
A02.24|
Salmonella osteomyelitis
A02.25|
Salmonella pyelonephritis
A02.29|
Salmonella with other localized infection
A02.8|
Other specified salmonella infections
A02.9|
Salmonella infection, unspecified
A03|
Shigellosis
A03.0|
Shigellosis due to Shigella dysenteriae
A03.1|
Shigellosis due to Shigella flexneri
A03.2|
Shigellosis due to Shigella boydii
A03.3|
Shigellosis due to Shigella sonnei
A03.8|
Other shigellosis
A03.9|
Shigellosis, unspecified
A04|
Other bacterial intestinal infections
A04.0|
Enteropathogenic Escherichia coli infection
A04.1|
Enterotoxigenic Escherichia coli infection
A04.2|
Enteroinvasive Escherichia coli infection
A04.3|
Enterohemorrhagic Escherichia coli infection
A04.4|
Other intestinal Escherichia coli infections
A04.5|
Campylobacter enteritis
A04.6|
Enteritis due to Yersinia enterocolitica
A04.7|
Enterocolitis due to Clostridium difficile
A04.71|
Enterocolitis due to Clostridium difficile, recurrent
A04.72|
Enterocolitis due to Clostridium difficile, not specified as recurrent
A04.8|
Other specified bacterial intestinal infections
A04.9|
Bacterial intestinal infection, unspecified

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