What is ICD-10 code B39.0?

B39.0 is the ICD-10-CM diagnosis code for Acute pulmonary histoplasmosis capsulati. A fungal lung infection caused by Histoplasma capsulatum that develops suddenly with acute symptoms like fever, cough, and chest discomfort. It belongs to the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99). B39.0 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. B39.0 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. B39.0 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. B39.0 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.

What is the V28 vs V24 difference for B39.0?

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. B39.0 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 should coders know when reporting B39.0?

Acute presentation typically occurs within weeks of exposure to contaminated soil or bird/bat droppings Document whether respiratory symptoms are present to support acute classification Because B39.0 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.

2026 ICD-10-CM B39.0: Acute pulmonary

ICD-10-CM Code View

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Code lookupB39.0Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Mycoses (B35-B49)

B39.0

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

Acute pulmonary histoplasmosis capsulati

A fungal lung infection caused by Histoplasma capsulatum that develops suddenly with acute symptoms like fever, cough, and chest discomfort.

Buddy Insight

Acute pulmonary histoplasmosis capsulati represents a significant endemic mycosis in the Ohio and Mississippi River valleys.

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

Mapped

HCC 163

HHS-HCC 163

Varies by metal level

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

B39Histoplasmosis

B39.0Acute pulmonary histoplasmosis capsulati

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for B39.0 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for B39.0 in this effective period.

Related Child Codes

Official

B39.1Chronic pulmonary histoplasmosis capsulati

B39.2Pulmonary histoplasmosis capsulati, unspecified

B39.3Disseminated histoplasmosis capsulati

B39.4Histoplasmosis capsulati, unspecified

B39.5Histoplasmosis duboisii

Includes

Official

ICD-10-CM does not list Includes notes for B39.0 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for B39.0 in this effective period.

Code First

Official

associated AIDS (B20)

Use Additional

Official

code for any associated manifestations, such as:
endocarditis (I39)
meningitis (G02)
pericarditis (I32)
retinitis (H32)

Code Also

Official

ICD-10-CM does not list Code Also instructions for B39.0 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Positive Histoplasma antigen (urine or serum) or culture confirmation

Acute onset of respiratory symptoms: fever, cough, malaise, chest pain

Chest imaging showing diffuse infiltrates, hilar lymphadenopathy, or miliary pattern

Exposure history (cave exploration, bird roosts, construction sites in endemic areas)

MEAT Support

HCC Buddy guidance

Positive Histoplasma antigen (urine or serum) or culture confirmation

Acute onset of respiratory symptoms: fever, cough, malaise, chest pain

Chest imaging showing diffuse infiltrates, hilar lymphadenopathy, or miliary pattern

Exposure history (cave exploration, bird roosts, construction sites in endemic areas)

Audit Caution

HCC Buddy guidance

Missing the diagnosis entirely when acute histoplasmosis presents as community-acquired pneumonia in endemic areas

Coding as unspecified (B39.2) when documentation clearly describes an acute presentation with defined onset

Not coding disseminated histoplasmosis (B39.3) when the infection has spread beyond the lungs to involve liver, spleen, or bone marrow

Common Mistakes

HCC Buddy guidance

B39.1 (Chronic pulmonary histoplasmosis capsulati) - chronic form shows cavitation and fibrosis; acute form shows infiltrates and adenopathy

B39.2 (Pulmonary histoplasmosis capsulati, unspecified) - use only when acute vs chronic cannot be determined

J18.9 (Pneumonia, unspecified) - histoplasmosis should be coded specifically when identified, not as generic pneumonia

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is B39.0 an HCC code?

Yes. B39.0 maps to Pneumococcal Pneumonia, Empyema, Lung Abscess under the V24 model but is not retained in V28.

Code: B39.0
Description: Acute pulmonary histoplasmosis capsulati
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 B39.0 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for B39.0

For B39.0to 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 B39.0 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

B39.0 is the ICD-10-CM diagnosis code for acute pulmonary histoplasmosis capsulati. A fungal lung infection caused by Histoplasma capsulatum that develops suddenly with acute symptoms like fever, cough, and chest discomfort. B39.0 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering mycoses (b35-b49).

Under the older CMS-HCC V24 model, B39.0 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.

Acute presentation typically occurs within weeks of exposure to contaminated soil or bird/bat droppings. Because B39.0 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 B39.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Acute presentation typically occurs within weeks of exposure to contaminated soil or bird/bat droppings
•Document whether respiratory symptoms are present to support acute classification

Clinical Significance

Acute pulmonary histoplasmosis capsulati represents a significant endemic mycosis in the Ohio and Mississippi River valleys. The acute form indicates recent exposure and active infection requiring distinct management from chronic disease. Accurate coding differentiates resource needs between acute self-limited disease and severe progressive infection requiring hospitalization.

Documentation Requirements

✓Positive Histoplasma antigen (urine or serum) or culture confirmation
✓Acute onset of respiratory symptoms: fever, cough, malaise, chest pain
✓Chest imaging showing diffuse infiltrates, hilar lymphadenopathy, or miliary pattern
✓Exposure history (cave exploration, bird roosts, construction sites in endemic areas)
✓Timeline establishing acute presentation versus chronic disease

Commonly Confused Codes

•B39.1 (Chronic pulmonary histoplasmosis capsulati) - chronic form shows cavitation and fibrosis; acute form shows infiltrates and adenopathy
•B39.2 (Pulmonary histoplasmosis capsulati, unspecified) - use only when acute vs chronic cannot be determined
•J18.9 (Pneumonia, unspecified) - histoplasmosis should be coded specifically when identified, not as generic pneumonia