A84.81 ICD-10-CM Code: Powassan virus disease
HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Viral and prion infections of the central nervous system (A80-A89)
A84.81
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidancePowassan virus disease
Powassan virus disease is a rare but serious infection transmitted by tick bites that causes inflammation of the brain and spinal cord, leading to symptoms like fever, headache, and neurological complications. This viral infection can result in long-term neurological damage or be life-threatening if severe.
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
N/A—
Not mapped
ACA/HHS
MappedHCC 3
Varies by metal level
ESRD/PACE
N/A—
Not mapped
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for A84.81 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for A84.81 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for A84.81 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for A84.81 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for A84.81 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for A84.81 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for A84.81 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 A84.81 an HCC code?
No. A84.81 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
A84.81 is the ICD-10-CM diagnosis code for powassan virus disease. Powassan virus disease is a rare but serious infection transmitted by tick bites that causes inflammation of the brain and spinal cord, leading to symptoms like fever, headache, and neurological complications. This viral infection can result in long-term neurological damage or be life-threatening if severe. A84.81 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering viral and prion infections of the central nervous system (a80-a89).
A84.81 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.
Verify the diagnosis is specifically documented as Powassan virus disease rather than other tick-borne illnesses like Lyme disease or other arboviral infections, as this affects code selection.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for A84.81 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify the diagnosis is specifically documented as Powassan virus disease rather than other tick-borne illnesses like Lyme disease or other arboviral infections, as this affects code selection
- •Look for documentation of complications such as encephalitis, meningitis, or other neurological manifestations, as these may require additional codes to fully capture the clinical picture