A85.8 ICD-10-CM Code: Other specified viral encephalitis
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)
A85.8
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceOther specified viral encephalitis
This code describes inflammation of the brain caused by a virus that is not one of the more common types (like West Nile virus or herpes). It is used when the specific viral cause has been identified but doesn't fit into other standard categories.
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
Official- Encephalitis lethargica
- Von Economo-Cruchet disease
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for A85.8 in this effective period.
Related Child Codes
Includes
Official- specified viral encephalomyelitis NEC
- specified viral meningoencephalitis NEC
Excludes 1
Official- encephalitis due to cytomegalovirus (B25.8)
- encephalitis due to herpesvirus NEC (B10.0-)
- encephalitis due to herpesvirus [herpes simplex] (B00.4)
- encephalitis due to measles virus (B05.0)
- encephalitis due to mumps virus (B26.2)
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for A85.8 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for A85.8 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for A85.8 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 A85.8 an HCC code?
No. A85.8 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
- Code
- A85.8
- Description
- Other specified viral encephalitis
- HCC (V28)
- No CMS-HCC V28 mapping
- RAF
- —
- Billable
- Yes
- Payment year
- 2026
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
A85.8 is the ICD-10-CM diagnosis code for other specified viral encephalitis. This code describes inflammation of the brain caused by a virus that is not one of the more common types (like West Nile virus or herpes). It is used when the specific viral cause has been identified but doesn't fit into other standard categories. A85.8 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).
A85.8 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.
Always verify the specific viral agent documented in the medical record and use more specific codes (A80-A87) when available, as A85.8 is reserved for 'other' viral encephalitis cases.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for A85.8 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Always verify the specific viral agent documented in the medical record and use more specific codes (A80-A87) when available, as A85.8 is reserved for 'other' viral encephalitis cases
- •Ensure the documentation clearly states 'encephalitis' (brain inflammation) rather than meningitis or other CNS conditions, and confirm viral etiology is established before coding