2027 ICD-10-CM Diagnosis Code B26.1Mumps meningitis

ICD-10-CM Codes›A00–B99›B25-B34›B26

ICD-10-CM B26.1
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

B26.1 is a billable ICD-10-CM diagnosis code for mumps meningitis. 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, 75 through 76, 791, 793. 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 62 closely related codes. Coders also document this condition as meningitis caused by mumps virus. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Meningitis and Viral infection.

Code Identity

ICD-10-CM Code
B26.1
Billable Status
Yes — Valid for Submission
Code Describes
Mumps meningitis
Short Description
Mumps meningitis
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 CodeB26.1Mumps meningitis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Meningitis caused by mumps virus
  • Meningitis caused by Paramyxovirus

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to B26.1: its own notes plus those printed at B26 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.

From B26 Mumps applies to 11 codes
  • epidemic parotitis
  • infectious parotitis
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 B26.1, its category, or a range that includes it.

Applicable To 1

These notes mention B26.1.

  • O98.5 Other viral diseases complicating pregnancy, childbirth and the puerperium
    Conditions in A80-B09, B25-B34, R87.81-, R87.82- names B25-B34, which includes this code

Excludes1 4

These codes carry an Excludes1 note naming B26.1: they are not reported together with it, unless the two conditions are unrelated.

  • A87 Viral meningitis
    meningitis due to mumps virus (B26.1)
  • G02 Meningitis in other infectious and parasitic diseases classified elsewhere
    mumps meningitis (B26.1)
  • K11.2 Sialoadenitis
    epidemic parotitis (B26.-) names B26.-, which includes this code
  • K11.2 Sialoadenitis
    mumps (B26.-) names B26.-, which includes this code

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 NVS001
Meningitis
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR INF008
Viral infection
Default principal diagnosis: inpatient No · outpatient No

Clinical InformationClinical

  • 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)

Patient EducationClinical

Meningitis

Meningitis is inflammation of the thin tissue that surrounds the brain and spinal cord, called the meninges. There are several types of meningitis. The most common is viral meningitis. You get it when a virus enters the body through the nose or mouth and travels to the brain. Bacterial meningitis is rare but can be deadly.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert B26.1 to ICD-9-CMHistory

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

ICD-9-CM
072.1 Mumps meningitis
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 B26.1Overview

What is the ICD-10 code for mumps meningitis?

The ICD-10-CM code for mumps meningitis is B26.1 (sometimes written as B261). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is B26.1 (Mumps) a billable code?

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

What MS-DRG does B26.1 group to?

When mumps meningitis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 793, 791, 24, 23, 75, 76, with relative weights from 0.8672 to 5.7422 depending on complications. Higher weights mean higher Medicare reimbursement.

Is B26.1 a CC or MCC?

CMS lists B26.1 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 62 closely related codes in its exclusion list.

What is the ICD-9 equivalent of B26.1?

Under the General Equivalence Mappings, mumps meningitis converts to ICD-9-CM 072.1 (mumps meningitis). The mapping is a direct match.