A79.81 ICD-10-CM Code: Rickettsiosis due to Ehrlichia sennetsu
A79.81 is not a CMS-HCC payment code. MEAT criteria · RAF Calculator · HCC coding software
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FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Rickettsioses (A75-A79)
A79.81
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceRickettsiosis due to Ehrlichia sennetsu
This is a bacterial infection caused by Ehrlichia sennetsu, a type of organism transmitted through tick bites that causes fever and flu-like symptoms. It is a form of rickettsiosis, which is a group of diseases caused by small parasitic bacteria.
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
N/A—
Not mapped
ESRD/PACE
N/A—
Not mapped
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
Official- Rickettsiosis due to Neorickettsia sennetsu
Excludes 2
Official- carrier or suspected carrier of infectious disease (Z22.-)Inherited from A00-B99
- infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)Inherited from A00-B99
- infectious and parasitic diseases specific to the perinatal period (P35-P39)Inherited from A00-B99
- influenza and other acute respiratory infections (J00-J22)Inherited from A00-B99
Related Codes
Includes
Official- diseases generally recognized as communicable or transmissibleInherited from A00-B99
Excludes 1
Official- certain localized infections - see body system-related chaptersInherited from A00-B99
Code First
OfficialNo Code First sequencing instructions are included in this display for A79.81. Check the code and parent instructions in the Code Book.
Use Additional
Official- code to identify resistance to antimicrobial drugs (Z16.-)Inherited from A00-B99
Code Also
OfficialNo Code Also instructions are included in this display for A79.81. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is A79.81 an HCC code?
No. A79.81 is a billable ICD-10-CM code with no mapping under the CMS-HCC V28 or V24 community payment models, and none under the ESRD, Part D RxHCC, or HHS-HCC models.
- Code
- A79.81
- Description
- Rickettsiosis due to Ehrlichia sennetsu
- HCC (V28)
- No CMS-HCC V28 mapping
- RAF reference coefficient
- —
- Billable
- Yes
- Payment year
- 2026
Coder workflow notes
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This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
A79.81 is the ICD-10-CM diagnosis code for rickettsiosis due to ehrlichia sennetsu. This is a bacterial infection caused by Ehrlichia sennetsu, a type of organism transmitted through tick bites that causes fever and flu-like symptoms. It is a form of rickettsiosis, which is a group of diseases caused by small parasitic bacteria. A79.81 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering rickettsioses (a75-a79).
A79.81 is a billable ICD-10-CM code, but the current payload does not show a mapping under the CMS-HCC V28 or V24 community payment models, and none under the ESRD, Part D RxHCC, or HHS-HCC models. Do not assign risk adjustment value from this page when no source-backed mapping is shown; verify the applicable model and payment year.
Verify documentation specifies Ehrlichia sennetsu as the causative organism, as other Ehrlichia species have different codes (A79.0 for Ehrlichia chaffeensis, A79.1 for Ehrlichia ewingii).
HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for A79.81 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify documentation specifies Ehrlichia sennetsu as the causative organism, as other Ehrlichia species have different codes (A79.0 for Ehrlichia chaffeensis, A79.1 for Ehrlichia ewingii)
- •Look for evidence of tick exposure or bite in the patient history, and consider coding the external cause if documented; this code should not be used if a different Ehrlichia species is identified