2027 ICD-10-CM Diagnosis Code B01.9Varicella without complication
ICD-10-CM Codes›A00–B99›B00-B09›B01
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Not Chronic
B01.9 is a billable ICD-10-CM diagnosis code for varicella without complication. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 791, 793, 865 through 866. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 23 closely related codes. Coders also document this condition as varicella. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Viral infection.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Varicella
- Varicella-zoster virus infection
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to B01.9: its own notes plus those printed at Chapter 1. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- diseases generally recognized as communicable or transmissible
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Varicella NOS
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- carrier or suspected carrier of infectious disease (Z22.-)
- certain localized infections - see body system-related chapters
- infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
- infectious and parasitic diseases specific to the perinatal period (P35-P39)
- influenza and other acute respiratory infections (J00-J22)
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify resistance to antimicrobial drugs (Z16.-)
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name B01.9, its category, or a range that includes it.
Excludes2 2
These codes carry an Excludes2 note naming B01.9: its condition is not part of those codes, and both may be reported when the patient has both.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Varicella B01.9
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Chickenpox
a highly contagious infectious disease caused by the varicella-zoster virus (herpesvirus 3, human). it usually affects children, is spread by direct contact or respiratory route via droplet nuclei, and is characterized by the appearance on the skin and mucous membranes of successive crops of typical pruritic vesicular lesions that are easily broken and become scabbed. chickenpox is relatively benign in children, but may be complicated by pneumonia and encephalitis in adults. (from dorland, 27th ed)
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 B01.9 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About B01.9Overview
What is the ICD-10 code for varicella without complication?
The ICD-10-CM code for varicella without complication is B01.9 (sometimes written as B019). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is B01.9 (Varicella [chickenpox]) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report varicella without complication on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does B01.9 group to?
When varicella without complication is the principal diagnosis on an inpatient stay, it groups to MS-DRG 793, 791, 866, 865, with relative weights from 0.8691 to 4.2192 depending on complications. Higher weights mean higher Medicare reimbursement.
Is B01.9 a CC or MCC?
CMS lists B01.9 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 23 closely related codes in its exclusion list.
What is the ICD-9 equivalent of B01.9?
Under the General Equivalence Mappings, varicella without complication converts to ICD-9-CM 052.9 (varicella uncomplicated). The mapping is a direct match.
