2026 ICD-10-CM Diagnosis Code B96.21Shiga toxin-producing Escherichia coli [E. coli] [STEC] O157 as the cause of diseases classified elsewhere

ICD-10-CM Codes›A00–B99›B95-B97›B96

ICD-10-CM B96.21
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

B96.21 is a billable ICD-10-CM diagnosis code for shiga toxin-producing Escherichia coli [E. coli] [STEC] O157 as the cause of diseases classified elsewhere. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 867 through 869. The code is not accepted as a principal diagnosis by the Medicare Code Editor. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections.

Code Identity

ICD-10-CM Code
B96.21
Billable Status
Yes — Valid for Submission
Code Describes
Shiga toxin-producing Escherichia coli [E. coli] [STEC] O157 as the cause of diseases classified elsewhere
Short Description
Shig tox E coli [STEC] O157 causing diseases classd elswhr
Parent Code
B96.2
Escherichia coli [E. coli ] as the cause of diseases classified elsewhere

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionB95-B97Bacterial and viral infectious agents
CategoryB96Other bacterial agents as the cause of diseases classified elsewhere
This CodeB96.21Shiga toxin-producing Escherichia coli [E. coli] [STEC] O157 as the cause of diseases classified elsewhere

Code EditsBilling

Medicare Code Editor checks that affect claim validity for B96.21.

Unacceptable principal diagnosis
There are selected codes that describe a circumstance which influences an individual's health status but not a current illness or injury, or codes that are not specific manifestations but may be due to an underlying cause. These codes are considered unacceptable as a principal diagnosis.

Tabular List NotesGuidance

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

Inclusion Terms

  • E. coli O157:H- (nonmotile) with confirmation of Shiga toxin
  • E. coli O157 with confirmation of Shiga toxin when H antigen is unknown, or is not H7
  • O157:H7 Escherichia coli E. coli with or without confirmation of Shiga toxin-production
  • Shiga toxin-producing Escherichia coli E. coli O157:H7 with or without confirmation of Shiga toxin-production
  • STEC O157:H7 with or without confirmation of Shiga toxin-production

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.

    • Escherichia coli(E. coli), as cause of disease classified elsewhere
      • O157
    • Escherichia coli(E. coli), as cause of disease classified elsewhere
      • O157 with confirmation of Shiga toxin when H antigen is unknown, or is not H7
    • Escherichia coli(E. coli), as cause of disease classified elsewhere
      • O157
    • Escherichia coli(E. coli), as cause of disease classified elsewhere
      • O157

Clinical ClassificationClinical

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

CCSR INF003
Bacterial infections
Default principal diagnosis: inpatient No · outpatient No

Patient EducationClinical

E. Coli Infections

E. coli is the name of a type of bacteria that lives in your intestines. Most types of E. coli are harmless. However, some types can make you sick and cause diarrhea. One type causes travelers' diarrhea. The worst type of E. coli causes bloody diarrhea, and can sometimes cause kidney failure and even death.

Read the full article at MedlinePlus

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

Convert B96.21 to ICD-9-CMHistory

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

ICD-9-CM
041.41 Shiga txn-produce E.coli
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 B96.21Overview

Is B96.21 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report shiga toxin-producing Escherichia coli [E. coli] [STEC] O157 as the cause of diseases classified elsewhere on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does B96.21 group to?

On inpatient claims, shiga toxin-producing Escherichia coli [E. coli] [STEC] O157 as the cause of diseases classified elsewhere maps to MS-DRG 867, 868, 869, with relative weights from 0.7297 to 2.0932 depending on complications. Higher weights mean higher Medicare reimbursement.

Can B96.21 be a principal diagnosis?

No. The Medicare Code Editor rejects this code as a principal diagnosis because shiga toxin-producing Escherichia coli [E. coli] [STEC] O157 as the cause of diseases classified elsewhere describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.

What is the ICD-9 equivalent of B96.21?

Under the General Equivalence Mappings, shiga toxin-producing Escherichia coli [E. coli] [STEC] O157 as the cause of diseases classified elsewhere converts to ICD-9-CM 041.41 (shiga txn-produce E.coli). 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.