2026 ICD-10-CM Diagnosis Code A22.1Pulmonary anthrax

ICD-10-CM Codes›A00–B99›A20-A28›A22

ICD-10-CM A22.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A22.1 is a billable ICD-10-CM diagnosis code for pulmonary anthrax. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 177 through 179. 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 132 closely related codes. Coders also document this condition as anthrax. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections and Pneumonia (except that caused by tuberculosis).

A22.1 no longer risk-adjusts for Medicare Advantage: it mapped to HCC 115 under the retired CMS-HCC V24 model through payment year 2025 but maps to no category in the live V28 model. It still risk-adjusts in the PACE (CMS-HCC V22) category 115, ESRD (V21) category 115, and ESRD (V24) category 115 for payment year 2026.

Code Identity

ICD-10-CM Code
A22.1
Billable Status
Yes — Valid for Submission
Code Describes
Pulmonary anthrax
Short Description
Pulmonary anthrax
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 CodeA22.1Pulmonary anthrax

Medicare Risk Adjustment (HCC)Billing

A22.1 no longer risk-adjusts for Medicare Advantage: it maps to no payment category in the live CMS-HCC V28 model, although it still risk-adjusts in the other CMS models shown below.

CMS-HCC V28 (Medicare Advantage Payment Model)
Not mapped
Dropped in V28 see all codes that no longer risk-adjust
Prior Model (CMS-HCC V24)
HCC 115
V24 retired last contributed to a Medicare Advantage risk score in payment year 2025
Other CMS Models
PACE (CMS-HCC V22): HCC 115 · ESRD (V21): HCC 115 · ESRD (V24): HCC 115
ESRD V21 weights: 0.013 dialysis, 0.143–0.155 functioning graft · ESRD V24 weights: 0.030 dialysis, 0.154–0.248 functioning graft
Part D (RxHCC)
Not mapped
A22.1 does not risk-adjust in the RxHCC prescription drug model

Source: CMS Payment Year 2026 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Anthrax
  • Anthrax pneumonia
  • Bacterial infection caused by Bacillus
  • Inhalational anthrax

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Inhalation anthrax
  • Ragpicker's disease
  • Woolsorter's disease

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 No · outpatient No
CCSR RSP002
Pneumonia (except that caused by tuberculosis)
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.

  • Anthrax Vaccines

    vaccines or candidate vaccines used to prevent anthrax.

  • Bacillus anthracis

    a species of bacteria that causes anthrax in humans and animals.

  • Anthrax

    an infection caused by bacillus anthracis bacteria. it may affect the lungs, gastrointestinal tract, or skin. patients with lung infection present with fever, headaches, cough, chest pain and shortness of breath. patients with gastrointestinal infection present with nausea, vomiting and bloody diarrhea. patients with skin infection develop blisters and ulcers.

  • Anthrax Toxin Receptor 1|ANTXR1|Tumor Endothelial Marker 8

    anthrax toxin receptor 1 (564 aa, ~63 kda) is encoded by the human antxr1 gene. this protein plays a role in the regulation of both cell adhesion and cellular motility.

  • ANTXR1 Gene|ANTXR1|ANTXR1|Anthrax Toxin Receptor 1 Gene

    this gene plays a role in cell-matrix adhesion.

  • ANTXR1 wt Allele|ATR|Anthrax Toxin Receptor 1 wt Allele|FLJ10601|FLJ21776|TEM8

    human antxr1 wild-type allele is located in the vicinity of 2p13.1 and is approximately 236 kb in length. this allele, which encodes anthrax toxin receptor 1 protein, is involved in the modulation of cytoskeletal rearrangement, cellular adhesion and cell migration. mutation of the gene is associated with hemangioma capillary infantile.

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 A22.1 to ICD-9-CMHistory

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

ICD-9-CM
022.1 Pulmonary anthrax
Approximate The match is approximate rather than exact.
ICD-9-CM
022.1 Pulmonary anthrax
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.
ICD-9-CM
484.5 Pneumonia in anthrax
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.

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 A22.1Overview

What is the ICD-10 code for pulmonary anthrax?

The ICD-10-CM code for pulmonary anthrax is A22.1 (sometimes written as A221). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is A22.1 (Anthrax) a billable code?

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

What MS-DRG does A22.1 group to?

When pulmonary anthrax is the principal diagnosis on an inpatient stay, it groups to MS-DRG 177, 178, 179, with relative weights from 0.7550 to 1.5627 depending on complications. Higher weights mean higher Medicare reimbursement.

Is A22.1 a CC or MCC?

CMS lists A22.1 as an MCC (major complication or comorbidity) for FY 2026. 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 132 closely related codes in its exclusion list.

What is the ICD-9 equivalent of A22.1?

Under the General Equivalence Mappings, pulmonary anthrax converts to ICD-9-CM 022.1 (pulmonary anthrax), 022.1 (pulmonary anthrax), and 484.5 (pneumonia in anthrax). The mapping is approximate, so confirm the match fits the documentation.

Does A22.1 risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage. A22.1 mapped to HCC 115 in the retired CMS-HCC V24 model, which last determined payment in 2025, but it maps to no category in the live V28 model; see all codes that no longer risk-adjust. It still risk-adjusts in the PACE (CMS-HCC V22) category 115 (Pneumococcal Pneumonia/Empyema/Lung Abscess), ESRD (V21) category 115 (Pneumococcal Pneumonia/Empyema/Lung Abscess), and ESRD (V24) category 115 (Pneumococcal Pneumonia/Empyema/Lung Abscess).