B96.21 ICD-10-CM Code: Shiga toxin-producing Escherichia coli [E. coli] [STEC] O157 as the cause of diseases classified elsewhere
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FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Bacterial and viral infectious agents (B95-B97)
B96.21
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceShiga toxin-producing Escherichia coli [E. coli] [STEC] O157 as the cause of diseases classified elsewhere
An infection caused by a specific strain of E. coli (O157) that produces Shiga toxin, commonly associated with severe diarrhea and hemolytic uremic syndrome.
CMS-HCC V28
00
RAF 0
CMS-HCC V24
00
RAF 0
ACA/HHS
00
RAF 0
ESRD/PACE
00
RAF 0
RXHCC
00
RAF 0
Code Trumping
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Code Book Path
Inclusion Terms
Official- 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
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for B96.21 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for B96.21 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for B96.21 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for B96.21 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for B96.21 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for B96.21 in this effective period.
Buddy Documentation Tip
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is B96.21 an HCC code?
No. B96.21 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
Coder workflow notes
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This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
B96.21 is the ICD-10-CM diagnosis code for shiga toxin-producing escherichia coli [e. coli] [stec] o157 as the cause of diseases classified elsewhere. An infection caused by a specific strain of E. coli (O157) that produces Shiga toxin, commonly associated with severe diarrhea and hemolytic uremic syndrome. B96.21 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering bacterial and viral infectious agents (b95-b97).
B96.21 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
O157:H7 is the most common pathogenic strain; document the specific serotype when available.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for B96.21 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •O157:H7 is the most common pathogenic strain; document the specific serotype when available
- •This organism is often foodborne and can cause life-threatening complications, particularly in children and elderly patients