Certain infectious and parasitic diseases
This chapter covers ICD-10-CM codes in the range A00-B99 for certain infectious and parasitic diseases. Covers bacterial, viral, and parasitic infections including tuberculosis, HIV, hepatitis, and other communicable diseases.
Chapter Overview
Key Statistics
- •Contains 22 categories and 891 total codes
- •Includes 829 billable codes and 62 non-billable codes
- •Chapter range: A00-B99
Clinical Relevance
Critical for coding infectious diseases, sepsis, and parasitic infections. Widely used in emergency medicine, infectious disease, and hospital settings for antimicrobial stewardship and infection control.
Documentation Requirements
Requires organism identification, infection site, antimicrobial resistance patterns, and severity indicators. Sepsis coding requires SIRS criteria documentation.
Special Considerations
Sequencing rules are critical - infectious organism code typically sequenced first, followed by manifestations. COVID-19 codes require specific documentation protocols.
Categories in this Chapter
Intestinal infectious diseases
Tuberculosis
Certain zoonotic bacterial diseases
Other bacterial diseases
Infections with a predominantly sexual mode of transmission
Other spirochetal diseases
Other diseases caused by chlamydiae
Rickettsioses
Viral and prion infections of the central nervous system
Arthropod-borne viral fevers and viral hemorrhagic fevers
Viral infections characterized by skin and mucous membrane lesions
Other human herpesviruses
Viral hepatitis
Human immunodeficiency virus [HIV] disease
Other viral diseases
Mycoses
Protozoal diseases
Helminthiases
Pediculosis, acariasis and other infestations
Sequelae of infectious and parasitic diseases
Bacterial and viral infectious agents
Other infectious diseases
Chapter-Specific Coding Guidelines
General Guidelines for Certain infectious and parasitic diseases:
- When coding infectious diseases, sequence the infectious organism code first, followed by the manifestation
- Use additional codes to identify resistance to antimicrobial drugs (Z16.-)
- Code also any associated sepsis (A41.9) when applicable
- Always code the most specific organism when laboratory confirmation is available
Documentation Requirements:
- •Specific organism identification when available from laboratory results
- •Site of infection must be clearly documented
- •Acute vs chronic status when applicable
- •Antimicrobial resistance patterns when known
- •Source of infection when relevant to treatment
Sequencing Rules:
- Primary infectious disease code should be sequenced first
- Manifestation codes follow the causal organism code
- Sepsis codes take precedence when systemic involvement is documented
- Multiple organisms require separate codes for each identified pathogen
When to Use:
- ✓When the infectious disease is the primary reason for the encounter
- ✓When documenting confirmed infectious diseases with laboratory confirmation
- ✓When coding both the infectious agent and its manifestations
- ✓For acute infectious conditions requiring immediate treatment
When NOT to Use:
- ✗Do not use for personal history of infectious disease (use Z87.- codes)
- ✗Do not use for exposure without infection (use Z20.- codes)
- ✗Do not use for carrier states (use Z22.- codes)
- ✗Avoid when condition is ruled out or suspected only
Special Considerations:
- ⚠COVID-19 cases require specific coding protocols
- ⚠Healthcare-associated infections need additional documentation
- ⚠Multi-drug resistant organisms require Z16.- codes
- ⚠Sepsis and severe sepsis have specific sequencing rules
Version Updates
The 2025 ICD-10-CM updates include significant changes to infectious disease coding, particularly for emerging pathogens, antimicrobial resistance, and post-infection conditions.
Recent Updates:
COVID-19 Long-term Effects Coding
Updated guidance for coding long COVID and post-COVID conditions with new U09.9 code usage
Impact: Affects coding of ongoing COVID-19 symptoms and complications
Enhanced Antimicrobial Resistance Coding
New codes for multidrug-resistant organisms and enhanced Z16.- category usage
Impact: Improved tracking of antibiotic resistance patterns
Implementation Guidance:
- •Review all infectious disease cases for appropriate organism-specific codes
- •Ensure proper sequencing of infectious disease and manifestation codes
- •Update documentation templates to capture antimicrobial resistance
- •Train coding staff on new COVID-19 long-term effect coding
Upcoming Changes:
- →Enhanced coding for emerging infectious diseases expected in 2026
- →Improved granularity for healthcare-associated infections
- →Potential new categories for climate-related infectious diseases
Related Resources
Essential resources for accurate infectious disease coding, clinical documentation, and staying current with epidemiological trends.
Official Documentation:
Related Chapters:
Frequently Asked Questions
How do I properly sequence codes when a patient has both an infectious organism and its manifestation?
Always code the infectious organism first, followed by the manifestation. For example, if a patient has pneumonia due to Streptococcus pneumoniae, code J13 first, then any additional manifestations.
When should I use sepsis codes versus specific infection codes?
Use sepsis codes (A41.-) when there is documented sepsis with SIRS. Use specific infection codes for localized infections without systemic involvement.
How do I handle antimicrobial resistance in my coding?
Use additional codes from category Z16.- to identify resistance to antimicrobial drugs when documented by the provider.