B33.1 ICD-10-CM Code: Ross River disease
HCC Buddy Code Card
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FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Other viral diseases (B25-B34)
B33.1
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceRoss River disease
Ross River disease is a viral infection transmitted by mosquitoes that causes joint pain, fever, and rash, primarily occurring in Australia and the Pacific region.
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- Epidemic polyarthritis and exanthema
- Ross River fever
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for B33.1 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for B33.1 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for B33.1 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for B33.1 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for B33.1 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for B33.1 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 B33.1 an HCC code?
No. B33.1 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
B33.1 is the ICD-10-CM diagnosis code for ross river disease. Ross River disease is a viral infection transmitted by mosquitoes that causes joint pain, fever, and rash, primarily occurring in Australia and the Pacific region. B33.1 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering other viral diseases (b25-b34).
B33.1 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.
Document the geographic location or travel history to Australia/Pacific region to support diagnosis.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for B33.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document the geographic location or travel history to Australia/Pacific region to support diagnosis
- •Specify any complications such as arthritis or persistent joint symptoms for more accurate coding