ICD-10 Code B04 – Monkeypox (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code B04 – Monkeypox
What it is
B04 identifies monkeypox, a viral infection caused by the monkeypox virus. Use it when the documentation confirms this diagnosis.
Clinical signs
Clinical features often include fever, headache, lymphadenopathy, and a characteristic rash that may progress through macules, papules, vesicles, and pustules. Clinical features vary; refer to documentation.
When to use this code
Use B04 when the provider documents monkeypox, orthopoxvirus infection, or a confirmed case of monkeypox. Code it from the final diagnosis, discharge summary, or other signed documentation. If the record only says “suspected,” check documentation.
Do not use for
Do not use B04 for nonspecific viral rash, chickenpox, or other rash illnesses without documented monkeypox. Do not code it from exposure alone or from an unconfirmed rule-out diagnosis.
Coding tip
Confirm that the chart states monkeypox explicitly; if the wording is unclear, check documentation before assigning B04.