ICD 10 Codes From A30-A49

The ICD-10-CM codes A30-A49 are considered to be a substantial part of Chapter I of ICD-10. This range of codes is labeled ‘Other Bacterial Diseases’ and includes a vast group of ailments, ranging from some of the deadliest infections in human history, such as leprosy or diphtheria, to contemporary cases of sepsis or Legionnaire’s disease.

For healthcare providers, as well as medical billers, it is quite important to know this range. Mostly, the conditions listed above pose a threat to life, which is why it is important to accurately document the conditions. To get a clearer insight into the manner by which these codes can be understood, you could refer to this resource on the structure of ICD-10 codes.

Chronic Mycobacterial Infections (A30–A31)

A30: Leprosy [Hansen’s Disease]

While rare in many developed nations, leprosy remains a significant health concern globally. It is caused by Mycobacterium leprae and primarily affects the skin, peripheral nerves, and upper respiratory tract.

• A30.0 Indeterminate leprosy: The early stage with few lesions.
• A30.3 Borderline leprosy: A clinically unstable form.
• A30.5 Lepromatous leprosy: The most severe form, characterized by widespread skin nodules and potential nerve damage.

A31: Infections due to other Mycobacteria

These are often referred to as “atypical” mycobacteria. Unlike tuberculosis, these organisms are typically found in the environment (soil and water).

• A31.0 Pulmonary mycobacterial infection: Frequently caused by Mycobacterium avium complex (MAC), especially in patients with underlying lung disease.
• A31.2 Disseminated mycobacterial infection: A common opportunistic infection in immunocompromised individuals, particularly those with advanced HIV/AIDS.

Vaccine-Preventable and Acute Bacterial Diseases (A32–A38)

A32: Listeriosis

Caused by Listeria monocytogenes, this is primarily a foodborne illness. It is particularly dangerous for pregnant women, newborns, and the elderly.

• A32.1 Listerial meningitis: A severe complication where the bacteria cross the blood-brain barrier.
• A32.7 Listerial sepsis: A systemic bloodstream infection.

A33–A35: Tetanus

Tetanus is caused by the toxin of Clostridium tetani, often entering the body through contaminated wounds.

• A33: Tetanus neonatorum: Tetanus in newborns, often due to unsterile umbilical cord care.
• A34: Obstetrical tetanus: Occurring during pregnancy or postpartum.
• A35: Other tetanus: The general code for “lockjaw” in the general population.

A36–A37: Diphtheria and Whooping Cough

• A36 Diphtheria: Characterized by a thick gray coating (pseudomembrane) in the throat, which can lead to airway obstruction.
• A37 Whooping Cough (Pertussis): Caused by Bordetella pertussis. Codes are differentiated by the species (e.g., A37.0 for B. pertussis vs. A37.1 for B. parapertussis).

A38: Scarlet Fever

Scarlet fever (Scarlatina) is a manifestation of Group A Streptococcus. It is coded here when the characteristic “sandpaper” rash accompanies a streptococcal sore throat.

Life-Threatening Systemic Infections (A39–A41)

This section contains some of the most critical codes in hospital billing and emergency medicine. This block sits within the broader ICD-10 codes A00-B99 category for infectious diseases.

A39: Meningococcal Infection

Caused by Neisseria meningitidis, these infections can progress with terrifying speed.

• A39.0 Meningococcal meningitis: Inflammation of the brain and spinal cord membranes.
• A39.2 Acute meningococcemia: A severe bloodstream infection that can cause rapid organ failure and skin necrosis (purpura fulminans).

A40–A41: Streptococcal and Other Sepsis

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection.

• A40 Streptococcal sepsis: Categorized by the specific group (e.g., A40.0 for Group A, A40.1 for Group B).
• A41 Other sepsis: This includes sepsis due to Staphylococcus aureus (A41.0), Escherichia coli (A41.51), and “Sepsis, unspecified organism” (A41.9).

Coding Note: Sepsis coding requires high clinical specificity. Documentation must distinguish between sepsis, severe sepsis (which requires an additional code from subcategory R65.2), and septic shock.

Specialized Bacterial Infections (A42–A48)

A42: Actinomycosis

A chronic infection caused by Actinomyces species, typically resulting in abscesses and draining sinuses in the jaw (lumpy jaw), thorax, or abdomen.

A43–A44: Nocardiosis and Bartonellosis

• A43 Nocardiosis: Often affects the lungs or skin; common in the immunocompromised.
• A44 Bartonellosis: Includes Carrion’s disease (A44.0) and other infections caused by Bartonella species.

A46: Erysipelas

A superficial bacterial skin infection (usually streptococcal) characterized by a sharply demarcated, shiny, red, and swollen area, most commonly on the legs or face.

A48: Other Bacterial Diseases, Not Elsewhere Classified

This “catch-all” category includes several distinct and important conditions:

• A48.1 Legionnaires’ disease: A severe form of pneumonia caused by Legionella pneumophila, often linked to contaminated water systems in large buildings.
• A48.3 Toxic shock syndrome (TSS): A severe reaction to toxins usually produced by Staphylococcus or Streptococcus.

The Role of Documentation and Technology

Accurately capturing the A30-A49 range requires detailed physician notes regarding the causative organism and the site of infection. In modern clinical settings, the use of what is EHR software has become indispensable for managing these codes. Electronic Health Records (EHRs) often include built-in prompts that help clinicians specify the type of sepsis or the specific strain of bacteria, ensuring that the final ICD-10 code reflects the true severity of the patient’s condition.

For more information on infectious disease coding and public health reporting, healthcare professionals can reference the CDC’s National Notifiable Diseases Surveillance System (NNDSS), which tracks many of the bacterial infections covered in this code range.

Summary Table: Key Codes in the A30–A49 Range

Conclusion

The A30-A49 code block covers a vast array of bacterial pathology. From the chronic management of leprosy to the emergency treatment of sepsis, these codes allow the global healthcare community to speak a universal language. For coders, the “Takeaway” is always specificity: whenever the lab results identify a specific organism, the code should move from a general “unspecified” category to the most precise code available in this range.