B25.9
BillableCytomegaloviral disease, unspecified
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is B25.9 an HCC code?
Yes. B25.9 maps to Opportunistic Infections under the CMS-HCC V28 risk adjustment model (and Opportunistic Infections under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. 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.
MEAT Criteria for B25.9
For B25.9 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 B25.9 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
B25.9 is the ICD-10-CM diagnosis code for cytomegaloviral disease, unspecified. A viral infection caused by cytomegalovirus (CMV) where the specific affected body part or system is not documented or identified. B25.9 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering other viral diseases (b25-b34).
Under the CMS-HCC V28 risk adjustment model, B25.9 maps to Opportunistic Infections (HCC 6) with a community, non-dual, aged base RAF weight of 0.439. Under the older V24 model, B25.9 mapped to the same category but with a base RAF weight of 0.440 — V28 recalibrated weights across the entire model. 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.
Use this code only when the documentation does not specify which organ system is affected by CMV; if a specific site is documented, use a more specific B25 code. Because B25.9 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 B25.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only when the documentation does not specify which organ system is affected by CMV; if a specific site is documented, use a more specific B25 code
- •Common in immunocompromised patients; review clinical context to determine if a more specific code applies
Clinical Significance
Cytomegaloviral disease, unspecified, is used when CMV infection is documented but the specific organ system affected is not identified. This code should prompt a query to the provider for site specification, as the clinical management and documentation quality improve with site-specific coding.
Documentation Requirements
- ✓Confirmed CMV infection (positive CMV PCR, culture, or antigen test)
- ✓Documentation that a specific organ involvement could not be determined
- ✓Clinical context: symptoms, immunocompromised status
- ✓Plans for further diagnostic workup to identify the affected organ system
- ✓Treatment regimen documented (empiric antiviral therapy)
Commonly Confused Codes
- •B25.0-B25.8 — Site-specific CMV codes; always prefer these over the unspecified code when organ involvement is documented
- •B27.10 (Cytomegaloviral mononucleosis without complications) — CMV mononucleosis in immunocompetent patients has a separate code
- •Z22.6 (Carrier of human T-lymphotropic virus type-1) — Different viral carrier state, not CMV