2026 ICD-10-CM Diagnosis Code B01.2Varicella pneumonia

ICD-10-CM Codes›A00–B99›B00-B09›B01

ICD-10-CM B01.2
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

B01.2 is a billable ICD-10-CM diagnosis code for varicella pneumonia. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 177 through 179, 791, 793. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 24 closely related codes. Coders also document this condition as chickenpox pneumonia. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Pneumonia (except that caused by tuberculosis) and Viral infection.

Code Identity

ICD-10-CM Code
B01.2
Billable Status
Yes — Valid for Submission
Code Describes
Varicella pneumonia
Short Description
Varicella pneumonia
Same as the full description in the CMS dataset.
Parent Code
B01
Varicella [chickenpox]

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionB00-B09Viral infections characterized by skin and mucous membrane lesions
CategoryB01Varicella [chickenpox]
This CodeB01.2Varicella pneumonia

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Chickenpox pneumonia
  • Hemorrhagic pneumonia
  • Hemorrhagic varicella pneumonia

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

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

CCSR RSP002
Pneumonia (except that caused by tuberculosis)
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR INF008
Viral infection
Default principal diagnosis: inpatient No · outpatient No

Patient EducationClinical

Chickenpox

Chickenpox is an infection caused by the varicella-zoster virus. Most cases are in children under age 15, but older children and adults can get it. It spreads very easily from one person to another.

Read the full article at MedlinePlus

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

Convert B01.2 to ICD-9-CMHistory

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

ICD-9-CM
052.1 Varicella pneumonitis
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 B01.2Overview

What is the ICD-10 code for varicella pneumonia?

The ICD-10-CM code for varicella pneumonia is B01.2 (sometimes written as B012). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is B01.2 (Varicella [chickenpox]) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report varicella pneumonia on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does B01.2 group to?

When varicella pneumonia is the principal diagnosis on an inpatient stay, it groups to MS-DRG 177, 178, 179, 791, 793, with relative weights from 0.7550 to 4.1696 depending on complications. Higher weights mean higher Medicare reimbursement.

Is B01.2 a CC or MCC?

CMS lists B01.2 as an MCC (major complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 24 closely related codes in its exclusion list.

What is the ICD-9 equivalent of B01.2?

Under the General Equivalence Mappings, varicella pneumonia converts to ICD-9-CM 052.1 (varicella pneumonitis). The mapping is a direct match.