2026 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 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A39.81 is a billable ICD-10-CM diagnosis code for meningococcal encephalitis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). 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

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Encephalitis(chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
      • meningococcal
    • Infection, infected, infective(opportunistic)
      • meningococcal
        • brain
    • Meningoencephalitis
      • epidemic
    • Meningomyelitis
      • meningococcal

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.

  • Neisseria meningitidis

    a species of gram-negative, aerobic bacteria. it is a commensal and pathogen only of humans, and can be carried asymptomatically in the nasopharynx. when found in cerebrospinal fluid it is the causative agent of cerebrospinal meningitis (meningitis, meningococcal). it is also found in venereal discharges and blood. there are at least 13 serogroups based on antigenic differences in the capsular polysaccharides; the ones causing most meningitis infections being a, b, c, y, and w-135. each serogroup can be further classified by serotype, serosubtype, and immunotype.

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 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About A39.81Overview

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, 2025 through September 30, 2026.

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.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.