What is ICD-10 code A22.1?

A22.1 is the ICD-10-CM diagnosis code for Pulmonary anthrax. It belongs to the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99). A22.1 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. A22.1 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. A22.1 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. A22.1 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does A22.1 map to under V28?

A22.1 does not map to a CMS-HCC V28 payment category. Check the current CMS-HCC V28 model file for payment year 2026 rather than an older V24 tip sheet.

What does A22.1 pay in RAF?

A22.1 has no separately stated V28 community RAF weight. If it is not a V28 payment HCC, it adds nothing to a community RAF score.

What is the V28 vs V24 difference for A22.1?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. A22.1 was a payment HCC under V24 (Pneumococcal Pneumonia, Empyema, Lung Abscess) but the V28 recalibration removed it from the risk adjustment model. Both models can still appear in legacy data and in payer-specific lookback periods.

What documentation supports A22.1?

Pulmonary anthrax is considered an infectious disease and may require reporting to public health authorities depending on jurisdiction; verify local reporting requirements Ensure documentation clearly specifies pulmonary involvement (as opposed to cutaneous or gastrointestinal anthrax) to support accurate code selection Because A22.1 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score. See the MEAT criteria checklist at /meat-criteria for what Monitor, Evaluate, Assess, or Treat looks like in a note. MEAT is generic documentation evidence, not a payer-specific rule.

2026 ICD-10-CM A22.1: Pulmonary anthrax

A22.1 is not a CMS-HCC payment code. MEAT criteria · RAF calculator · free HCC coding tools

ICD-10-CM Code View

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Code lookupA22.1Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Certain zoonotic bacterial diseases (A20-A28)

A22.1

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Pulmonary anthrax

Pulmonary anthrax is a serious lung infection caused by breathing in spores from the anthrax bacterium, which can cause severe respiratory illness and pneumonia-like symptoms. This is a rare but potentially life-threatening condition that requires immediate medical treatment with antibiotics.

Buddy Insight

Pulmonary anthrax (inhalational anthrax) is the most lethal form of Bacillus anthracis infection with historically near-100% mortality if untreated.

CMS-HCC V28

N/A

—

Not risk-adjusted for this model/period.

Not mapped

CMS-HCC V24

Mapped

HCC 115

Pneumococcal Pneumonia, Empye...

RAF 0.130

ACA/HHS

N/A

—

Not risk-adjusted for this model/period.

Not mapped

ESRD/PACE

Mapped

HCC 115

Pneumococcal Pneumonia, Empye...

RAF 0.030

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

A22Anthrax

A22.1Pulmonary anthrax

Inclusion Terms

Official

Inhalation anthrax
Ragpicker's disease
Woolsorter's disease

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for A22.1 in this effective period.

Related Child Codes

Official

A22.0Cutaneous anthrax

A22.2Gastrointestinal anthrax

A22.7Anthrax sepsis

A22.8Other forms of anthrax

A22.9Anthrax, unspecified

Includes

Official

infection due to Bacillus anthracis

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for A22.1 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for A22.1 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for A22.1 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for A22.1 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Clinical presentation consistent with inhalational anthrax (widened mediastinum on imaging, hemorrhagic pleural effusions, respiratory failure)

Laboratory confirmation — blood cultures, PCR, or anthrax-specific testing (lethal factor, protective antigen)

Chest imaging (CT preferred) showing mediastinal widening, pleural effusions, or pulmonary infiltrates

Epidemiologic investigation findings (occupational exposure, mail handling, bioterrorism assessment)

MEAT Support

HCC Buddy guidance

Clinical presentation consistent with inhalational anthrax (widened mediastinum on imaging, hemorrhagic pleural effusions, respiratory failure)

Laboratory confirmation — blood cultures, PCR, or anthrax-specific testing (lethal factor, protective antigen)

Chest imaging (CT preferred) showing mediastinal widening, pleural effusions, or pulmonary infiltrates

Epidemiologic investigation findings (occupational exposure, mail handling, bioterrorism assessment)

Audit Caution

HCC Buddy guidance

Inhalational anthrax presents initially with flu-like symptoms followed by rapid deterioration — early documentation may not reflect the ultimate severity

Anthrax meningitis (A22.8) commonly accompanies pulmonary anthrax — code both when documented

Do not assign A22.1 for cutaneous anthrax with incidental respiratory symptoms — reserve for true pulmonary involvement

Common Mistakes

HCC Buddy guidance

A22.0 (Cutaneous anthrax) — Cutaneous is the most common natural form with skin lesion (eschar); A22.1 is specifically respiratory tract involvement

A22.7 (Anthrax sepsis) — Code A22.7 when anthrax progresses to septicemia; if both pulmonary and sepsis are present, code both

J15.9 (Unspecified bacterial pneumonia) — Never use generic pneumonia codes for confirmed anthrax pneumonia

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is A22.1 an HCC code?

Yes. A22.1 maps to Pneumococcal Pneumonia, Empyema, Lung Abscess under the V24 model but is not retained in V28.

Code: A22.1
Description: Pulmonary anthrax
HCC (V28): No CMS-HCC V28 mapping
RAF: —
Billable: Yes
Payment year: 2026

HCC Category Mapping

V24HCC 115, Pneumococcal Pneumonia, Empyema, Lung Abscess

0.130

ESRDHCC 115, Pneumococcal Pneumonia, Empyema, Lung Abscess

0.030

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work A22.1 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for A22.1

For A22.1 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed A22.1 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

A22.1 is the ICD-10-CM diagnosis code for pulmonary anthrax. Pulmonary anthrax is a serious lung infection caused by breathing in spores from the anthrax bacterium, which can cause severe respiratory illness and pneumonia-like symptoms. This is a rare but potentially life-threatening condition that requires immediate medical treatment with antibiotics. A22.1 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering certain zoonotic bacterial diseases (a20-a28).

Under the older CMS-HCC V24 model, A22.1 maps to Pneumococcal Pneumonia, Empyema, Lung Abscess (HCC 115) with a community, non-dual, aged base RAF weight of 0.130. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Pulmonary anthrax is considered an infectious disease and may require reporting to public health authorities depending on jurisdiction; verify local reporting requirements. Because A22.1 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for A22.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Pulmonary anthrax is considered an infectious disease and may require reporting to public health authorities depending on jurisdiction; verify local reporting requirements
•Ensure documentation clearly specifies pulmonary involvement (as opposed to cutaneous or gastrointestinal anthrax) to support accurate code selection

Clinical Significance

Pulmonary anthrax (inhalational anthrax) is the most lethal form of Bacillus anthracis infection with historically near-100% mortality if untreated. It is a CDC Category A bioterrorism agent and a national security concern. Even with aggressive treatment, mortality remains 45-90%, making early recognition critical.

Documentation Requirements

✓Clinical presentation consistent with inhalational anthrax (widened mediastinum on imaging, hemorrhagic pleural effusions, respiratory failure)
✓Laboratory confirmation — blood cultures, PCR, or anthrax-specific testing (lethal factor, protective antigen)
✓Chest imaging (CT preferred) showing mediastinal widening, pleural effusions, or pulmonary infiltrates
✓Epidemiologic investigation findings (occupational exposure, mail handling, bioterrorism assessment)
✓Public health notification and coordination documentation

Commonly Confused Codes

•A22.0 (Cutaneous anthrax): Cutaneous is the most common natural form with skin lesion (eschar); A22.1 is specifically respiratory tract involvement
•A22.7 (Anthrax sepsis): Code A22.7 when anthrax progresses to septicemia; if both pulmonary and sepsis are present, code both
•J15.9 (Unspecified bacterial pneumonia): Never use generic pneumonia codes for confirmed anthrax pneumonia