ICD-10 A86
Billable / Specific CCUnspecified viral encephalitis
About ICD-10-CM A86
ICD-10-CM code A86 represents Unspecified viral encephalitis. This is a billable/specific code in the Infectious and Parasitic Diseases chapter (block A86). The 2026 edition of ICD-10-CM A86 became effective on October 1, 2025.
Coding Tips for A86
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
A86 is designated CC for MS-DRG grouping. On inpatient claims, this code can shift the DRG to the with-CC variant when documented as a present-on-admission secondary diagnosis. Hospital CDI programs flag CC opportunities during chart review. Failure to capture this code may leave 30 to 80 percent of the inpatient stay revenue unrealized.
Inclusion Terms / Approximate Synonyms
Clinical terms and conditions classified under A86. Per CMS ICD-10-CM Tabular 2026.
- Viral encephalomyelitis NOS
- Viral meningoencephalitis NOS
Inpatient DRG Impact, CC
codes Unspecified viral encephalitis. As a Complication/Comorbidity (CC), this contributes to DRG severity adjustment when documented alongside the principal diagnosis.
Medicare LCD Coverage for A86
Local Coverage Determinations (LCDs) from CMS MACs that list A86 as a covered diagnosis.
Showing top 10 of 549 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing A86.
2 Cigna
5 Medicare
CPT Codes Commonly Billed with A86
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
- G2189 CMS LCD: Billing and Coding: CT of the Head CMS LCD
- G2194 CMS LCD: Billing and Coding: CT of the Head CMS LCD
- G2193 CMS LCD: Billing and Coding: CT of the Head CMS LCD
- G2187 CMS LCD: Billing and Coding: CT of the Head CMS LCD
- G2188 CMS LCD: Billing and Coding: CT of the Head CMS LCD
- G2191 CMS LCD: Billing and Coding: CT of the Head CMS LCD
- G2190 CMS LCD: Billing and Coding: CT of the Head CMS LCD
- G2192 CMS LCD: Billing and Coding: CT of the Head CMS LCD
- G2195 CMS LCD: Billing and Coding: CT of the Head CMS LCD
Convert A86 to ICD-9-CM
Per CMS General Equivalence Mappings (GEMs), useful for legacy data review and historical claim analysis.
| ICD-10 | ICD-9 | Mapping Flags |
|---|---|---|
| A86 | 0499 | 10000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To A86
Other codes in section A80-A89 (Viral and prion infections of the central nervous system).
ICD-10 A86, Billing FAQ
Is ICD-10 code A86 billable? +
Yes, A86 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
What other names or terms map to A86? +
ICD-10 A86 includes: Viral encephalomyelitis NOS; Viral meningoencephalitis NOS.
Is A86 a CC or MCC for inpatient DRG? +
Yes, this code is designated as CC. Documenting as a secondary diagnosis on inpatient claims can shift the DRG to a higher-weighted category.
What CPT codes are commonly billed with A86? +
Procedures frequently paired with A86 include: G2189, G2194, G2193, G2187, G2188.
What ICD-9 codes does A86 map to? +
Per CMS GEMs, A86 maps to ICD-9 codes: 0499. Useful for legacy data review and historical claim analysis.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on June 1, 2026.
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