2026 ICD-10-CM Diagnosis Code A23.9Brucellosis, unspecified

ICD-10-CM Codes›A00–B99›A20-A28›A23

ICD-10-CM A23.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A23.9 is a billable ICD-10-CM diagnosis code for brucellosis, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 867 through 869. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 6 closely related codes. Coders also document this condition as brucella infection of the central nervous system. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections.

Code Identity

ICD-10-CM Code
A23.9
Billable Status
Yes — Valid for Submission
Code Describes
Brucellosis, unspecified
Short Description
Brucellosis, unspecified
Same as the full description in the CMS dataset.
Parent Code
A23
Brucellosis

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA20-A28Certain zoonotic bacterial diseases
CategoryA23Brucellosis
This CodeA23.9Brucellosis, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Brucella infection of the central nervous system
  • Brucella spondylitis
  • Brucellosis
  • Brucellosis of skin
  • Brucellosis uveitis

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 Yes · outpatient Yes

Clinical InformationClinical

  • Brucellosis

    infection caused by bacteria of the genus brucella mainly involving the mononuclear phagocyte system. this condition is characterized by fever, weakness, malaise, and weight loss.

  • Brucellosis, Bovine

    a disease of cattle caused by bacteria of the genus brucella leading to abortion in late pregnancy. brucella abortus is the primary infective agent.

Patient EducationClinical

Animal Diseases and Your Health

Animal diseases that people can catch are called zoonoses. Many diseases affecting humans can be traced to animals or animal products. You can get a disease directly from an animal, or indirectly, through the environment.

Read the full article at MedlinePlus

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

Convert A23.9 to ICD-9-CMHistory

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

ICD-9-CM
023.9 Brucellosis NOS
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 A23.9Overview

What is the ICD-10 code for brucellosis, unspecified?

The ICD-10-CM code for brucellosis, unspecified is A23.9 (sometimes written as A239). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is A23.9 (Brucellosis) a billable code?

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

What MS-DRG does A23.9 group to?

When brucellosis, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 867, 868, 869, with relative weights from 0.7297 to 2.0932 depending on complications. Higher weights mean higher Medicare reimbursement.

Is A23.9 a CC or MCC?

CMS lists A23.9 as a CC (complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 6 closely related codes in its exclusion list.

What is the ICD-9 equivalent of A23.9?

Under the General Equivalence Mappings, brucellosis, unspecified converts to ICD-9-CM 023.9 (brucellosis NOS). The mapping is a direct match.