A92.31 ICD-10-CM Code: West Nile virus infection with encephalitis
HCC Buddy Code Card
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FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Arthropod-borne viral fevers and viral hemorrhagic fevers (A90-A99)
A92.31
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceWest Nile virus infection with encephalitis
West Nile virus infection that has spread to cause inflammation of the brain (encephalitis). This is a serious neurological complication of West Nile virus transmitted through mosquito bites.
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- West Nile encephalitis
- West Nile encephalomyelitis
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for A92.31 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for A92.31 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for A92.31 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for A92.31 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for A92.31 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for A92.31 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 A92.31 an HCC code?
No. A92.31 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
A92.31 is the ICD-10-CM diagnosis code for west nile virus infection with encephalitis. West Nile virus infection that has spread to cause inflammation of the brain (encephalitis). This is a serious neurological complication of West Nile virus transmitted through mosquito bites. A92.31 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering arthropod-borne viral fevers and viral hemorrhagic fevers (a90-a99).
A92.31 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.
Ensure documentation clearly states both the West Nile virus infection AND encephalitis diagnosis before assigning this code; encephalitis must be explicitly documented as a complication.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for A92.31 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Ensure documentation clearly states both the West Nile virus infection AND encephalitis diagnosis before assigning this code; encephalitis must be explicitly documented as a complication
- •Do not use this code for West Nile virus without encephalitis; use A92.30 instead for uncomplicated West Nile virus infection