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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A05|
Other bacterial foodborne intoxications, not elsewhere classified
A05.0|
Foodborne staphylococcal intoxication
A05.1|
Botulism food poisoning
A05.2|
Foodborne Clostridium perfringens [Clostridium welchii] intoxication
A05.3|
Foodborne Vibrio parahaemolyticus intoxication
A05.4|
Foodborne Bacillus cereus intoxication
A05.5|
Foodborne Vibrio vulnificus intoxication
A05.8|
Other specified bacterial foodborne intoxications
A05.9|
Bacterial foodborne intoxication, unspecified
A06|
Amebiasis
A06.0|
Acute amebic dysentery
A06.1|
Chronic intestinal amebiasis
A06.2|
Amebic nondysenteric colitis
A06.3|
Ameboma of intestine
A06.4|
Amebic liver abscess
A06.5|
Amebic lung abscess
A06.6|
Amebic brain abscess
A06.7|
Cutaneous amebiasis
A06.8|
Amebic infection of other sites
A06.81|
Amebic cystitis
A06.82|
Other amebic genitourinary infections
A06.89|
Other amebic infections
A06.9|
Amebiasis, unspecified
A07|
Other protozoal intestinal diseases
A07.0|
Balantidiasis
A07.1|
Giardiasis [lambliasis]
A07.2|
Cryptosporidiosis
A07.3|
Isosporiasis
A07.4|
Cyclosporiasis
A07.8|
Other specified protozoal intestinal diseases
A07.9|
Protozoal intestinal disease, unspecified
A08|
Viral and other specified intestinal infections
A08.0|
Rotaviral enteritis
A08.1|
Acute gastroenteropathy due to Norwalk agent and other small round viruses
A08.11|
Acute gastroenteropathy due to Norwalk agent
A08.19|
Acute gastroenteropathy due to other small round viruses
A08.2|
Adenoviral enteritis
A08.3|
Other viral enteritis
A08.31|
Calicivirus enteritis
A08.32|
Astrovirus enteritis
A08.39|
Other viral enteritis
A08.4|
Viral intestinal infection, unspecified
A08.8|
Other specified intestinal infections
A09|
Infectious gastroenteritis and colitis, unspecified
A15|
Respiratory tuberculosis
A15.0|
Tuberculosis of lung
A15.4|
Tuberculosis of intrathoracic lymph nodes
A15.5|
Tuberculosis of larynx, trachea and bronchus
A15.6|
Tuberculous pleurisy
A15.7|
Primary respiratory tuberculosis

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