2026 ICD-10-CM Diagnosis Code B26.2Mumps encephalitis

ICD-10-CM Codes›A00–B99›B25-B34›B26

ICD-10-CM B26.2
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

B26.2 is a billable ICD-10-CM diagnosis code for mumps encephalitis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). Coders also document this condition as meningitis caused by mumps virus. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Encephalitis and Viral infection.

Code Identity

ICD-10-CM Code
B26.2
Billable Status
Yes — Valid for Submission
Code Describes
Mumps encephalitis
Short Description
Mumps encephalitis
Same as the full description in the CMS dataset.
Parent Code
B26
Mumps

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionB25-B34Other viral diseases
CategoryB26Mumps
This CodeB26.2Mumps encephalitis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Meningitis caused by mumps virus
  • Meningitis caused by Paramyxovirus
  • Meningoencephalitis caused by virus
  • Mumps encephalitis
  • Mumps meningoencephalitis
  • Paramyxoviridae 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)
      • in (due to)
        • mumps
    • Meningoencephalitis
      • in (due to)
        • mumps
    • Meningoencephalitis
      • mumps
    • Mumps
      • encephalitis
    • Mumps
      • meningoencephalitis

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NVS002
Encephalitis
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR INF008
Viral infection
Default principal diagnosis: inpatient No · outpatient No

Clinical InformationClinical

  • Measles-Mumps-Rubella Vaccine

    a combined vaccine used to prevent measles; mumps; and rubella.

  • Mumps

    an acute infectious disease caused by rubulavirus, spread by direct contact, airborne droplet nuclei, fomites contaminated by infectious saliva, and perhaps urine, and usually seen in children under the age of 15, although adults may also be affected. (from dorland, 28th ed)

  • Mumps Vaccine

    vaccines used to prevent infection by mumps virus. best known is the live attenuated virus vaccine of chick embryo origin, used for routine immunization of children and for immunization of adolescents and adults who have not had mumps or been immunized with live mumps vaccine. children are usually immunized with measles-mumps-rubella combination vaccine.

  • Mumps virus

    the type species of rubulavirus that causes an acute infectious disease in humans, affecting mainly children. transmission occurs by droplet infection.

  • Viral Fusion Proteins

    proteins, usually glycoproteins, found in the viral envelopes of a variety of viruses. they promote cell membrane fusion and thereby may function in the uptake of the virus by cells.

  • Rubulavirus

    a genus of the family paramyxoviridae (subfamily paramyxovirinae) where all the species have hemagglutinin and neuraminidase activities but lack a c protein. mumps virus is the type species.

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 B26.2 to ICD-9-CMHistory

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

ICD-9-CM
072.2 Mumps 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 B26.2Overview

Is B26.2 (Mumps) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report mumps encephalitis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What is the ICD-9 equivalent of B26.2?

Under the General Equivalence Mappings, mumps encephalitis converts to ICD-9-CM 072.2 (mumps 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.