ICD-10 Code J21.1 – Acute bronchiolitis due to human metapneumovirus (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code J21.1 – Acute bronchiolitis due to human metapneumovirus
What it is
J21.1 identifies acute bronchiolitis caused by human metapneumovirus, a viral lower respiratory infection that primarily affects the small airways. Use it when the record clearly links bronchiolitis to this specific virus.
Clinical signs
Typical findings include cough, wheezing, tachypnea, and increased work of breathing, often with signs of viral respiratory illness. Clinical features vary; refer to documentation.
When to use this code
Use this code when the clinician documents acute bronchiolitis due to human metapneumovirus, or when the diagnosis is confirmed in the chart. You should code it for encounters focused on this infection, including emergency, inpatient, or outpatient visits. Check documentation if the virus is not specified.
Do not use for
Do not use J21.1 for bronchiolitis caused by another organism or for unspecified acute bronchiolitis. If the record only says viral respiratory infection or pneumonia, code the documented condition instead.
Coding tip
Assign J21.1 only when human metapneumovirus is explicitly documented as the cause.