Question 1

What is ICD-10 code A75.9?

Accepted Answer

A75.9 is the ICD-10-CM diagnosis code for typhus fever, unspecified. Typhus fever is a serious infectious disease spread by lice, fleas, or mites that causes high fever, headache, and rash. This code is used when the specific type of typhus cannot be determined or is not documented. A75.9 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering rickettsioses (a75-a79).

A75.9 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.

Use this unspecified code only when the medical record does not specify the type of typhus (epidemic, endemic, or scrub typhus); query the provider if more specific documentation is available.

Question 2

Is A75.9 an HCC code?

Accepted Answer

No. A75.9 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 A75.9 billable?

Accepted Answer

Yes. A75.9 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. A75.9 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 A75.9?

Accepted Answer

A75.9 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 A75.9 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 A75.9?

Accepted Answer

Use this unspecified code only when the medical record does not specify the type of typhus (epidemic, endemic, or scrub typhus); query the provider if more specific documentation is available Ensure the patient has confirmed typhus fever diagnosis; do not use this code for suspected cases without confirmation, and verify the causative organism or vector if documented

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A75.9

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A75.9 ICD-10-CM Code: Typhus fever, unspecified

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A75.9

Is A75.9 an HCC code?

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