ICD-10 Code B34.9 – Viral infection, unspecified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code B34.9 – Viral infection, unspecified
What it is
B34.9 identifies a viral infection when the specific virus is not documented or cannot be confirmed. Use it for a nonspecific viral illness that does not fit a more precise code.
Clinical signs
Clinical features vary; refer to documentation. Commonly recorded findings may include fever, malaise, upper respiratory symptoms, or other nonspecific viral complaints without an identified organism.
When to use this code
Use B34.9 when the clinician documents a viral infection but does not name the virus and no more specific code is available. It also fits cases where testing is negative or not performed, and the record supports a viral illness. Code the documented site or manifestation separately if instructed by the record.
Do not use for
Do not use this code when a specific viral infection is documented, such as influenza or COVID-19. Also avoid it if the condition is clearly a symptom-only presentation or another diagnosis better explains the encounter.
Coding tip
If the note names the virus or a related syndrome, check for a more specific ICD-10 code before defaulting to B34.9.