2026 ICD-10-CM Diagnosis Code J21.0Acute bronchiolitis due to respiratory syncytial virus

ICD-10-CM Codes›J00–J99›J20-J22›J21

ICD-10-CM J21.0
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

J21.0 is a billable ICD-10-CM diagnosis code for acute bronchiolitis due to respiratory syncytial virus. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 202 through 203. Coders also document this condition as acute bronchiolitis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Acute bronchitis and Viral infection.

Code Identity

ICD-10-CM Code
J21.0
Billable Status
Yes — Valid for Submission
Code Describes
Acute bronchiolitis due to respiratory syncytial virus
Short Description
Acute bronchiolitis due to respiratory syncytial virus
Same as the full description in the CMS dataset.
Parent Code
J21
Acute bronchiolitis

Code Classification

ChapterJ00–J99Diseases of the respiratory system
SectionJ20-J22Other acute lower respiratory infections
CategoryJ21Acute bronchiolitis
This CodeJ21.0Acute bronchiolitis due to respiratory syncytial virus

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute bronchiolitis
  • Acute bronchiolitis caused by respiratory syncytial virus
  • Acute lower respiratory infection caused by respiratory syncytial virus
  • Acute viral bronchiolitis
  • Respiratory syncytial virus bronchiolitis

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Acute bronchiolitis due to RSV

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Bronchiolitis(acute) (infective) (subacute)
      • due to
        • respiratory syncytial virus (RSV)
    • Infection, infected, infective(opportunistic)
      • virus, viral NOS
        • respiratory syncytial (RSV)
          • bronchiolitis
    • Virus, viral
      • respiratory syncytial (RSV)
        • bronchiolitis

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR RSP005
Acute bronchitis
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR INF008
Viral infection
Default principal diagnosis: inpatient No · outpatient No

Clinical InformationClinical

  • Acute Bronchiolitis

    acute inflammation of the bronchioles usually caused by the respiratory syncytial virus.

Patient EducationClinical

Bronchial Disorders

When you breathe in, the air travels down through your trachea (windpipe). It then goes through two tubes to your lungs. These tubes are your bronchi. Bronchial disorders can make it hard for you to breathe.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert J21.0 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
466.11 Acu broncholitis d/t RSV
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About J21.0Overview

Is J21.0 (Acute bronchiolitis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report acute bronchiolitis due to respiratory syncytial virus on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does J21.0 group to?

When acute bronchiolitis due to respiratory syncytial virus is the principal diagnosis on an inpatient stay, it groups to MS-DRG 202, 203, with relative weights from 0.6700 to 0.9712 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of J21.0?

Under the General Equivalence Mappings, acute bronchiolitis due to respiratory syncytial virus converts to ICD-9-CM 466.11 (acu broncholitis d/t RSV). The mapping is a direct match.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.