A78 ICD-10-CM Code: Q fever
HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Rickettsioses (A75-A79)
A78
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceQ fever
Q fever is a contagious infection caused by bacteria that spreads through contact with infected animals or contaminated materials, causing flu-like symptoms such as fever, chills, and fatigue. It can affect the lungs, heart, and other organs if left untreated.
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
N/A—
Not mapped
ACA/HHS
N/A—
Not mapped
ESRD/PACE
N/A—
Not mapped
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
Official- Infection due to Coxiella burnetii
- Nine Mile fever
- Quadrilateral fever
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for A78 in this effective period.
Related Child Codes
ICD-10-CM does not list child codes under A78 for this display context.
Includes
OfficialICD-10-CM does not list Includes notes for A78 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for A78 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for A78 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for A78 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for A78 in this effective period.
Buddy Documentation Tip
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is A78 an HCC code?
No. A78 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
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
A78 is the ICD-10-CM diagnosis code for q fever. Q fever is a contagious infection caused by bacteria that spreads through contact with infected animals or contaminated materials, causing flu-like symptoms such as fever, chills, and fatigue. It can affect the lungs, heart, and other organs if left untreated. A78 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering rickettsioses (a75-a79).
A78 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.
Q fever is a reportable disease in most jurisdictions; verify local reporting requirements when assigning this code.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for A78 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Q fever is a reportable disease in most jurisdictions; verify local reporting requirements when assigning this code
- •Distinguish between acute Q fever (A78) and chronic Q fever (B90.9 or other chronic manifestations) as they have different treatment approaches and clinical outcomes