ICD-10 Code A48.1 – Legionnaires’ disease (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A48.1 – Legionnaires’ disease
What it is
Use this code for Legionnaires’ disease, a serious form of pneumonia caused by Legionella infection. It represents a specific infectious diagnosis, not nonspecific pneumonia or exposure alone.
Clinical signs
Typical findings include fever, cough, shortness of breath, and radiographic pneumonia. Clinical features vary; refer to documentation for confirmed Legionella infection or physician-documented Legionnaires’ disease.
When to use this code
Assign A48.1 when the provider documents Legionnaires’ disease, Legionella pneumonia, or confirmed Legionella infection causing pneumonia. Use it only when the diagnosis is established in the record, not for suspected exposure or pending test results.
If the chart says pneumonia due to Legionella, this code is appropriate. Check documentation when the note only mentions atypical pneumonia or respiratory infection without a clear Legionella diagnosis.
Do not use for
Do not use this code for Legionella exposure, carrier status, or pneumonia without documented Legionella involvement. If the diagnosis is uncertain, check documentation.
Coding tip
Look for the provider’s final diagnostic statement; microbiology alone does not replace clear clinical documentation.