ICD-10 Code J11.82 – Influenza due to unidentified influenza virus with myocarditis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code J11.82 – Influenza due to unidentified influenza virus with myocarditis
What it is
This code identifies influenza caused by an unidentified influenza virus when myocarditis is documented. Use it for a flu illness with heart muscle inflammation, not for influenza without cardiac involvement.
Clinical signs
Clinical features vary; refer to documentation. Myocarditis may be supported by chest pain, shortness of breath, palpitations, fatigue, or abnormal cardiac testing noted by the clinician.
When to use this code
Use J11.82 when the provider documents influenza and explicitly links it to myocarditis. The influenza virus is not identified as a specific type or strain in the record. If the chart only says flu with heart symptoms, check documentation before coding.
Do not use for
Do not use this code for influenza with a documented virus type such as seasonal or novel influenza. Do not assign it when myocarditis is absent or when the record does not clearly connect the myocarditis to influenza.
Coding tip
Verify both elements in the note: influenza and myocarditis, with an unspecified influenza virus source.