2027 ICD-10-CM Diagnosis Code A39.81Meningococcal encephalitis

ICD-10-CM Codes›A00–B99›A30-A49›A39

ICD-10-CM A39.81
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

A39.81 is a billable ICD-10-CM diagnosis code for meningococcal encephalitis. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 23 through 24, 94 through 96. 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 10 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections and Encephalitis.

Code Identity

ICD-10-CM Code
A39.81
Billable Status
Yes — Valid for Submission
Code Describes
Meningococcal encephalitis
Short Description
Meningococcal encephalitis
Same as the full description in the CMS dataset.
Parent Code
A39.8
Other meningococcal infections

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA30-A49Other bacterial diseases
CategoryA39Meningococcal infection
This CodeA39.81Meningococcal encephalitis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Meningococcal encephalitis

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to A39.81: its own notes plus those printed at 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.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • diseases generally recognized as communicable or transmissible

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.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • 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.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • 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 A39.81, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming A39.81: they are not reported together with it, unless the two conditions are unrelated.

  • G05 Encephalitis, myelitis and encephalomyelitis in diseases classified elsewhere
    meningococcal encephalitis, myelitis and encephalomyelitis (A39.81)

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.

CCSR INF003
Bacterial infections
Default principal diagnosis: inpatient No · outpatient No
CCSR NVS002
Encephalitis
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Meningococcal Infections

    infections with bacteria of the species neisseria meningitidis.

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 A39.81 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
036.1 Meningococc encephalitis
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About A39.81Overview

What is the ICD-10 code for meningococcal encephalitis?

The ICD-10-CM code for meningococcal encephalitis is A39.81 (sometimes written as A3981). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is A39.81 (Other meningococcal infections) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report meningococcal encephalitis on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does A39.81 group to?

When meningococcal encephalitis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 24, 23, 96, 95, 94, with relative weights from 2.3173 to 5.7422 depending on complications. Higher weights mean higher Medicare reimbursement.

Is A39.81 a CC or MCC?

CMS lists A39.81 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 10 closely related codes in its exclusion list.

What is the ICD-9 equivalent of A39.81?

Under the General Equivalence Mappings, meningococcal encephalitis converts to ICD-9-CM 036.1 (meningococc encephalitis). The mapping is a direct match.