2027 ICD-10-CM Diagnosis Code A22.9Anthrax, unspecified

ICD-10-CM Codes›A00–B99›A20-A28›A22

ICD-10-CM A22.9
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

A22.9 is a billable ICD-10-CM diagnosis code for anthrax, unspecified. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) 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 anthrax. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections.

Code Identity

ICD-10-CM Code
A22.9
Billable Status
Yes — Valid for Submission
Code Describes
Anthrax, unspecified
Short Description
Anthrax, unspecified
Same as the full description in the CMS dataset.
Parent Code
A22
Anthrax

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA20-A28Certain zoonotic bacterial diseases
CategoryA22Anthrax
This CodeA22.9Anthrax, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Anthrax
  • Anthrax manifestation
  • Bacterial infection caused by Bacillus

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to A22.9: its own notes plus those printed at A22 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 A22 Anthrax applies to 6 codes
  • infection due to Bacillus anthracis
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.

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

  • Anthrax

    an acute infection caused by the spore-forming bacteria bacillus anthracis. it commonly affects hoofed animals such as sheep and goats. infection in humans often involves the skin (cutaneous anthrax), the lungs (inhalation anthrax), or the gastrointestinal tract. anthrax is not contagious and can be treated with antibiotics.

Patient EducationClinical

Anthrax

Anthrax is a disease caused by Bacillus anthracis, a germ that lives in soil. Many people know about it from the 2001 bioterror attacks. In the attacks, someone purposely spread anthrax through the U.S. mail. This killed five people and made 22 sick.

Read the full article at MedlinePlus

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

Convert A22.9 to ICD-9-CMHistory

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

ICD-9-CM
022.9 Anthrax 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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About A22.9Overview

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

The ICD-10-CM code for anthrax, unspecified is A22.9 (sometimes written as A229). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is A22.9 (Anthrax) a billable code?

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

What MS-DRG does A22.9 group to?

When anthrax, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 867, 869, 868, with relative weights from 0.6784 to 2.1855 depending on complications. Higher weights mean higher Medicare reimbursement.

Is A22.9 a CC or MCC?

CMS lists A22.9 as a CC (complication or comorbidity) for FY 2027. 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 A22.9?

Under the General Equivalence Mappings, anthrax, unspecified converts to ICD-9-CM 022.9 (anthrax NOS). The mapping is a direct match.