2027 ICD-10-CM Diagnosis Code A85.8Other specified viral encephalitis
ICD-10-CM Codes›A00–B99›A80-A89›A85
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Not Chronic
A85.8 is a billable ICD-10-CM diagnosis code for other specified viral encephalitis. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 97 through 99, 974 through 976. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 188 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Encephalitis and Viral infection.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Arbovirus encephalitis
- Arenavirus encephalitis
- Australian bat lyssavirus encephalitis
- BK polyomavirus encephalitis
- Borna virus encephalitis
- Bunyaviridae encephalitis
- Cache Valley virus infection
- Coxsackie virus encephalitis
- Coxsackievirus infection of the central nervous system
- Disease caused by BK polyomavirus
- Disease caused by Deltaretrovirus
- Disease caused by Filoviridae
- Disease caused by Flaviviridae
- Disease caused by Hantanvirus
- Disease caused by Hantavirus
- Disease caused by Nairovirus
- Disease caused by Vesiculovirus
- Encephalitis caused by Alphavirus
- Encephalitis caused by European subtype of tick-borne encephalitis virus
- Encephalitis caused by Hantaan virus
- Encephalitis caused by Hendra virus
- Encephalitis caused by Lagos bat virus
- Encephalitis caused by Langat virus
- Encephalitis caused by Nipah virus
- Encephalitis caused by Polyomavirus
- Encephalitis caused by Rubulavirus
- Encephalitis caused by tick-borne encephalitis virus
- Encephalitis caused by Vesiculovirus
- Encephalitis caused by Vilyuisk human encephalitis virus
- Encephalitis lethargica
- Enteroviral neurological disease
- Epstein Barr virus infection of the central nervous system
- Epstein-Barr virus encephalitis
- Filovirus encephalitis
- Flavivirus encephalitis
- Hendra virus infection
- Henipavirus encephalitis
- Human immunodeficiency virus encephalitis
- Human T-lymphotropic virus 1 infection
- Human T-lymphotropic virus 2 infection
- Human T-lymphotropic virus type 1 encephalitis
- Human T-lymphotropic virus type 2 encephalitis
- Infection caused by Henipavirus
- Infection caused by Human T-lymphotropic virus
- Infection caused by Lymphocytic choriomeningitis virus
- Infection caused by Nipah virus
- Infection caused by Rubulavirus
- Invasive viral infectious disease
- Kumlinge virus encephalitis
- Kyasanur Forest disease virus encephalitis
- Louping ill virus encephalitis
- Lymphocytic choriomeningitis virus encephalitis
- Mokola virus disease
- Mokola virus encephalitis
- Morbillivirus encephalitis
- Nairoviral encephalitis
- Negishi encephalitis
- Neuroinvasive Cache Valley encephalitis virus infection
- Neuroinvasive Cache Valley virus disease
- Orthopoxvirus encephalitis
- Paramyxoviridae encephalitis
- Parechovirus encephalitis
- Puumala virus encephalitis
- Respiratory syncytial virus encephalitis
- Retroviridae encephalitis
- Rhabdovirus encephalitis
- Rift valley fever
- Rift Valley virus encephalitis
- Rio Bravo fever
- Rio Bravo viral encephalitis
- Tensaw encephalitis
- Tensaw virus disease
- Thogoto virus disease
- Toscana virus encephalitis
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to A85.8: its own notes plus those printed at A85, block A80-A89, and Chapter 1. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- specified viral encephalomyelitis NEC
- specified viral meningoencephalitis NEC
- diseases generally recognized as communicable or transmissible
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Encephalitis lethargica
- Von Economo-Cruchet disease
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
- 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)
- encephalitis due to poliomyelitis virus (A80.-)
- encephalitis due to zoster (B02.0)
- lymphocytic choriomeningitis (A87.2)
- myalgic encephalomyelitis (G93.32)
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- carrier or suspected carrier of infectious disease (Z22.-)
- certain localized infections - see body system-related chapters
- infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
- infectious and parasitic diseases specific to the perinatal period (P35-P39)
- influenza and other acute respiratory infections (J00-J22)
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify resistance to antimicrobial drugs (Z16.-)
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Cruchet's disease A85.8
Economo's disease A85.8
Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute) G04.90
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Encephalitis
Encephalitis is inflammation (swelling) of the brain. It can happen when an infection or medical condition that affects the brain activates your immune system. The inflammation can cause a wide range of symptoms. In extreme cases, it can lead to brain damage, stroke, or even death.
The full article covers:
- What is encephalitis?
- What causes encephalitis?
- Who is more likely to get encephalitis?
- What are the symptoms of encephalitis?
- How is encephalitis diagnosed?
- What are the treatments for encephalitis?
- Can encephalitis be prevented?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert A85.8 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About A85.8Overview
What is the ICD-10 code for other specified viral encephalitis?
The ICD-10-CM code for other specified viral encephalitis is A85.8 (sometimes written as A858). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is A85.8 (Other viral encephalitis, not elsewhere classified) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report other specified viral encephalitis on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does A85.8 group to?
When other specified viral encephalitis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 98, 974, 976, 99, 975, 97, with relative weights from 0.7879 to 3.8208 depending on complications. Higher weights mean higher Medicare reimbursement.
Is A85.8 a CC or MCC?
CMS lists A85.8 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 188 closely related codes in its exclusion list.
Can A85.8 be reported with B25.8?
Not as a rule. The Excludes1 note at A85, which applies to A85.8, lists "encephalitis due to cytomegalovirus (B25.8)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
