A84.0 ICD-10-CM Code: Far Eastern tick-borne encephalitis [Russian spring-summer encephalitis]
HCC Buddy Code Card
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FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Viral and prion infections of the central nervous system (A80-A89)
A84.0
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceFar Eastern tick-borne encephalitis [Russian spring-summer encephalitis]
This is a serious brain infection caused by a virus transmitted through tick bites, primarily occurring in Russia and Far Eastern regions during spring and summer months. The infection causes inflammation of the brain and can lead to fever, headache, and neurological complications.
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 A84.0 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for A84.0 in this effective period.
Related Child Codes
Includes
Official- tick-borne viral meningoencephalitis
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for A84.0 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for A84.0 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for A84.0 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for A84.0 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 A84.0 an HCC code?
No. A84.0 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
A84.0 is the ICD-10-CM diagnosis code for far eastern tick-borne encephalitis [russian spring-summer encephalitis]. This is a serious brain infection caused by a virus transmitted through tick bites, primarily occurring in Russia and Far Eastern regions during spring and summer months. The infection causes inflammation of the brain and can lead to fever, headache, and neurological complications. A84.0 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).
A84.0 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.
This code is specific to the Far Eastern variant of tick-borne encephalitis; do not use for other geographic variants of tick-borne encephalitis which have separate codes (A84.1 for Central European tick-borne encephalitis).
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for A84.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code is specific to the Far Eastern variant of tick-borne encephalitis; do not use for other geographic variants of tick-borne encephalitis which have separate codes (A84.1 for Central European tick-borne encephalitis)
- •Document the geographic location and season of exposure when available, as this supports the specificity of the diagnosis and may be relevant for epidemiological tracking