A78 Q fever

The ICD-10-CM code for Q fever is A78 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

1: Certain infectious and parasitic diseases (A00-B99)

Section

A75-A79: Rickettsioses (A75-A79)

Category A78

1 code (1 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to A78:

• Q fever
• Quadrilateral fever
• Balkan grippe
• Endocarditis (chronic) (marantic) (nonbacterial) (thrombotic) (valvular) › Q fever
• Fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor) › Australian Q
• Fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor) › Nine-Mile
• Endocarditis (chronic) (marantic) (nonbacterial) (thrombotic) (valvular) › Coxiella burnetii
• Australian › Q fever

Inclusion Terms

• Infection due to Coxiella burnetii
• Nine Mile fever
• Quadrilateral fever

U.S. Hospital Utilization

• An estimated 330 U.S. inpatient stays in 2023 included A78 among the documented diagnoses.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

Official Coding Guidelines

HIV Infections (TOC entry)

a. Human Immunodeficiency Virus (HIV) Infections .............................................................. 19

Infectious agents causing diseases in other chapters (TOC)

b. Infectious agents as the cause of diseases classified to other chapters ................................. 22

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool
• AHRQ — HCUP National Inpatient Sample, Frequencies by Diagnosis Code (2016–2023)