A28.9 ICD-10-CM Code: Zoonotic bacterial disease, unspecified
HCC Buddy Code Card
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FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Certain zoonotic bacterial diseases (A20-A28)
A28.9
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceZoonotic bacterial disease, unspecified
This code is used when a patient has a bacterial infection acquired from animals or animal products, but the specific type of zoonotic disease cannot be determined or identified. It serves as a catch-all diagnosis for animal-related bacterial infections that don't fit into more specific disease categories.
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
OfficialICD-10-CM does not list inclusion terms for A28.9 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for A28.9 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for A28.9 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for A28.9 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for A28.9 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for A28.9 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for A28.9 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 A28.9 an HCC code?
No. A28.9 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
A28.9 is the ICD-10-CM diagnosis code for zoonotic bacterial disease, unspecified. This code is used when a patient has a bacterial infection acquired from animals or animal products, but the specific type of zoonotic disease cannot be determined or identified. It serves as a catch-all diagnosis for animal-related bacterial infections that don't fit into more specific disease categories. A28.9 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering certain zoonotic bacterial diseases (a20-a28).
A28.9 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.
Use this code only when the specific zoonotic bacterial disease cannot be identified; always attempt to obtain more specific diagnostic information from the provider before defaulting to the unspecified code.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for A28.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only when the specific zoonotic bacterial disease cannot be identified; always attempt to obtain more specific diagnostic information from the provider before defaulting to the unspecified code
- •Review the patient's exposure history and clinical presentation documented in the medical record, as this may help identify a more specific zoonotic disease code (such as brucellosis A23.x, leptospirosis A27.x, or Q fever A78)