ICD-10 Code A78 – Q fever (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A78 – Q fever
What it is
A78 identifies Q fever, an infection caused by Coxiella burnetii. It is usually acquired from exposure to infected animals or contaminated dust and may present as an acute febrile illness or a chronic infection.
Clinical signs
Clinical features vary; refer to documentation. Commonly reported findings include fever, headache, myalgia, and atypical pneumonia or hepatitis in acute disease. Chronic Q fever may involve endocarditis or other persistent focal infection.
When to use this code
Use A78 when the provider documents Q fever, Coxiella burnetii infection, or a confirmed clinical diagnosis of this condition. Code it for acute or chronic disease when the record clearly supports Q fever as the reason for care. Check documentation if the note only mentions exposure or suspicion.
Do not use for
Do not use A78 for nonspecific fever, pneumonia, or hepatitis without documentation linking them to Q fever. It is also not appropriate for past exposure alone or for a ruled-out infection.
Coding tip
Assign A78 only when the provider names Q fever or documents Coxiella burnetii infection; otherwise, code the confirmed manifestation.