2027 ICD-10-CM Diagnosis Code A92.31West Nile virus infection with encephalitis
ICD-10-CM Codes›A00–B99›A90-A99›A92
- Billable — Valid for Submission
- MCC — Major Complication or Comorbidity
- Not Chronic
A92.31 is a billable ICD-10-CM diagnosis code for West Nile virus infection with encephalitis. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 865 through 866. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 131 closely related codes. Coders also document this condition as disease caused by West Nile virus. 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.
- Disease caused by West Nile virus
- Disorder of nervous system caused by West Nile virus
- West Nile encephalitis
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to A92.31: its own notes plus those printed at A92 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.
- 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.
- West Nile encephalitis
- West Nile encephalomyelitis
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
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.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name A92.31, its category, or a range that includes it.
Excludes1 1
These codes carry an Excludes1 note naming A92.31: they are not reported together with it, unless the two conditions are unrelated.
- A85.2 Arthropod-borne viral encephalitis, unspecifiedWest nile virus with encephalitis (A92.31)
Excludes2 2
These codes carry an Excludes2 note naming A92.31: its condition is not part of those codes, and both may be reported when the patient has both.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
West Nile Fever
a mosquito-borne viral illness caused by the west nile virus, a flavivirus and endemic to regions of africa, asia, and europe. common clinical features include headache; fever; maculopapular rash; gastrointestinal symptoms; and lymphadenopathy. meningitis; encephalitis; and myelitis may also occur. the disease may occasionally be fatal or leave survivors with residual neurologic deficits. (from joynt, clinical neurology, 1996, ch26, p13; lancet 1998 sep 5;352(9130):767-71)
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 A92.31 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About A92.31Overview
What is the ICD-10 code for West Nile virus infection with encephalitis?
The ICD-10-CM code for West Nile virus infection with encephalitis is A92.31 (sometimes written as A9231). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is A92.31 (West Nile virus infection) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report West Nile virus infection with encephalitis on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does A92.31 group to?
When West Nile virus infection with encephalitis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 866, 865, with relative weights from 0.8691 to 1.3153 depending on complications. Higher weights mean higher Medicare reimbursement.
Is A92.31 a CC or MCC?
CMS lists A92.31 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 131 closely related codes in its exclusion list.
Can A92.31 be reported with B33.1?
Not as a rule. The Excludes1 note at A92, which applies to A92.31, lists "Ross River disease (B33.1)". 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).
