ICD-10-CM 2027
ICD-10 code for Q fever
From the official ICD-10-CM alphabetic index entry “Fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor) › Q”. Page updated September 29, 2026.
About coding Q fever
The ICD-10-CM code for Q fever is A78 (Q fever).
As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.
In MS-DRG v44.0, it is part of the grouping logic for DRG 867 (Other Infectious and Parasitic Diseases Diagnoses with MCC, relative weight 2.1859), DRG 868 (Other Infectious and Parasitic Diseases Diagnoses with CC, relative weight 1.0235) and DRG 869 (Other Infectious and Parasitic Diseases Diagnoses without CC/MCC, relative weight 0.6787), in MDC 18 (Infectious and Parasitic Diseases, Systemic or Unspecified Sites), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.
Common questions about Q fever ICD-10 codes
What is the ICD-10 code for Q fever?
- A78 — Q fever.
Is A78 billable?
- Yes. A78 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can A78 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict A78 as a principal diagnosis.
Is A78 a CC or MCC?
- A78 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.