ICD-10 Code B33 – Other viral diseases, not elsewhere classified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code B33 – Other viral diseases, not elsewhere classified
What it is
B33 is a broad ICD-10-CM category for viral illnesses that do not fit a more specific diagnosis. Use it when the record identifies a viral disease, but documentation does not support a more precise code.
Clinical signs
Clinical features vary; refer to documentation. You may see nonspecific viral symptoms such as fever, malaise, fatigue, rash, or upper-respiratory complaints, but the chart must support a viral disease diagnosis.
When to use this code
Use B33 when the provider documents an “other viral disease” and no more specific ICD-10-CM code applies. It is appropriate when the organism or syndrome is confirmed as viral, but the condition is not indexed elsewhere.
Do not assign it for a suspected viral illness without confirmation or for common viral infections with their own specific codes. Check documentation for the exact diagnosis, site, and any related manifestation.
Do not use for
Do not use B33 for influenza, viral hepatitis, herpesviral infections, or other specifically coded viral diseases. Also avoid it when the record only says “viral syndrome” or “rule out viral infection.”
Coding tip
Before coding B33, verify that no more specific viral diagnosis is documented or indexed in the chart.