B09 ICD-10-CM Code: Unspecified viral infection characterized by skin and mucous membrane lesions
HCC Buddy Code Card
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FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Viral infections characterized by skin and mucous membrane lesions (B00-B09)
B09
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceUnspecified viral infection characterized by skin and mucous membrane lesions
A viral infection that causes blisters, sores, or other lesions on the skin and inside the mouth or other body openings, but the specific virus causing it has not been identified.
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- Viral enanthema NOS
- Viral exanthema NOS
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for B09 in this effective period.
Related Child Codes
ICD-10-CM does not list child codes under B09 for this display context.
Includes
OfficialICD-10-CM does not list Includes notes for B09 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for B09 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for B09 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for B09 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for B09 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 B09 an HCC code?
No. B09 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
B09 is the ICD-10-CM diagnosis code for unspecified viral infection characterized by skin and mucous membrane lesions. A viral infection that causes blisters, sores, or other lesions on the skin and inside the mouth or other body openings, but the specific virus causing it has not been identified. B09 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering viral infections characterized by skin and mucous membrane lesions (b00-b09).
B09 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 viral agent cannot be determined; if the virus is identified, use a more specific code.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for B09 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 viral agent cannot be determined; if the virus is identified, use a more specific code
- •Document any associated symptoms or affected body areas to support medical necessity