2026 ICD-10-CM Diagnosis Code B66.4Paragonimiasis
ICD-10-CM Codes›A00–B99›B65-B83›B66
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Not Chronic
B66.4 is a billable ICD-10-CM diagnosis code for paragonimiasis. 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 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 8 closely related codes. Coders also document this condition as extrapulmonary paragonimiasis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Parasitic, other specified and unspecified infections.
B66.4 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
Code Classification
Medicare Risk Adjustment (HCC)Billing
B66.4 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.
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.
- Extrapulmonary paragonimiasis
- Generalized paragonimiasis
- Infection by Paragonimus
- Infection by Paragonimus kellicotti
- Infection caused by Paragonimus westermani
- Paragonimus granuloma
- Paragonimus larva migrans
- Visceral larva migrans syndrome
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- Infection due to Paragonimus species
- Lung fluke disease
- Pulmonary distomiasis
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Disease, diseased See Also: Syndrome;
Oriental lung fluke B66.4
lung (oriental) B66.4
Paragonimus (westermani) B66.4
Paragonimiasis B66.4
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Paragonimiasis
infection with trematoda of the genus paragonimus.Paragonimiasis
a parasitic infection caused by trematodes of the paragonimus genus. humans are infected from ingestion of raw or undercooked food. it results in chronic lung infection and eosinophilia.
Patient EducationClinical
Parasitic Diseases
Parasites are living things that use other living things - like your body - for food and a place to live. You can get them from contaminated food or water, a bug bite, or sexual contact. Some parasitic diseases are easily treated and some are not.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert B66.4 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About B66.4Overview
What is the ICD-10 code for paragonimiasis?
The ICD-10-CM code for paragonimiasis is B66.4 (sometimes written as B664). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is B66.4 (Other fluke infections) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report paragonimiasis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does B66.4 group to?
When paragonimiasis 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 B66.4 a CC or MCC?
CMS lists B66.4 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 8 closely related codes in its exclusion list.
What is the ICD-9 equivalent of B66.4?
Under the General Equivalence Mappings, paragonimiasis converts to ICD-9-CM 121.2 (paragonimiasis). The mapping is a direct match.
Does B66.4 risk-adjust for Medicare Advantage payment?
Not for Medicare Advantage. B66.4 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).
