Question 1

What is ICD-10 code Z20.821?

Accepted Answer

Z20.821 is the ICD-10-CM diagnosis code for contact with and (suspected) exposure to zika virus. A person has had contact with or suspected exposure to Zika virus, a mosquito-borne infection. Z20.821 sits in the ICD-10-CM chapter for factors influencing health status and contact with health services (z00-z99), within the section covering persons with potential health hazards related to communicable diseases (z20-z29).

Z20.821 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.

Particularly important to document in pregnant women due to birth defect risks.

Question 2

Is Z20.821 an HCC code?

Accepted Answer

No. Z20.821 is a billable ICD-10-CM code but does not map to any payment HCC category under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can still be reported on Medicare Advantage encounter data submissions, but it does not contribute to the beneficiary's Risk Adjustment Factor (RAF) score and therefore does not affect the risk-adjusted capitation payment to the plan. V28 reached 100% phase-in for payment year 2026.

Question 3

Is Z20.821 billable?

Accepted Answer

Yes. Z20.821 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. Z20.821 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.

Question 4

What is the V28 vs V24 difference for Z20.821?

Accepted Answer

Z20.821 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither model rewards Z20.821 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a payment HCC.

Question 5

What should coders know when reporting Z20.821?

Accepted Answer

Particularly important to document in pregnant women due to birth defect risks Include travel history and exposure circumstances when available

Z20.821

Is Z20.821 an HCC code?

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Open Z20.821 in the Interactive Encoder