ICD-10 Code B01 – Varicella [chickenpox] (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code B01 – Varicella [chickenpox]
What it is
B01 identifies varicella, commonly called chickenpox, an acute viral infection caused by varicella-zoster virus. It is used when the diagnosis is confirmed or documented as chickenpox.
Clinical signs
Typical findings include an itchy, generalized vesicular rash that appears in crops and progresses through macules, papules, and crusts. Fever and malaise may occur; clinical features vary, so refer to documentation.
When to use this code
Use B01 when the record states chickenpox or varicella as the diagnosis. It also fits encounters for active disease, uncomplicated or complicated, when no more specific subcategory is documented. If the note mentions a varicella complication, code that condition as directed by the record.
Do not use for
Do not use B01 for herpes zoster, which is shingles, or for a history of varicella without current illness. Check documentation if the rash is only suspected or another viral exanthem is listed.
Coding tip
Confirm whether the provider documented active varicella, a complication, or only exposure/history before assigning B01.