2026 ICD-10-CM Diagnosis Code A78Q fever

ICD-10-CM Codes›A00–B99›A75-A79›A78

ICD-10-CM A78
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A78 is a billable ICD-10-CM diagnosis code for q fever. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 867 through 869. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 56 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections.

Code Identity

ICD-10-CM Code
A78
Billable Status
Yes — Valid for Submission
Code Describes
Q fever
Short Description
Q fever
Same as the full description in the CMS dataset.
Chapter
A75-A79
Rickettsioses

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA75-A79Rickettsioses
CategoryA78Q fever
This CodeA78Q fever

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute Q fever
  • Bacterial hepatitis
  • Bacterial osteomyelitis
  • Chronic Q fever
  • Encephalomyelitis caused by bacterium
  • Encephalomyelitis caused by Coxiella burnetii
  • Infection caused by Coxiella
  • Infection causing encephalomyelitis
  • Meningitis caused by Coxiella burnetii
  • Myelitis caused by bacterium
  • Pneumonia in Q fever
  • Q fever
  • Q fever encephalitis
  • Q fever endocarditis
  • Q fever hepatitis
  • Q fever myocarditis
  • Q fever osteomyelitis
  • Q fever pericarditis

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

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

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INF003
Bacterial infections
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Q Fever

    an acute infectious disease caused by coxiella burnetii. it is characterized by a sudden onset of fever; headache; malaise; and weakness. in humans, it is commonly contracted by inhalation of infected dusts derived from infected domestic animals (animals, domestic).

  • Q Fever

    a bacterial infection caused by coxiella burnetii. it is transmitted to humans by the inhalation of infected air particles or contact with fluids and feces of infected animals. signs and symptoms include the abrupt onset of fever, headache, myalgias, and weakness.

  • Aseptic Meningitis

    inflammation of the membranes surrounding the brain and spinal cord without a bacterial pathogen.

Patient EducationClinical

Animal Diseases and Your Health

Animal diseases that people can catch are called zoonoses. Many diseases affecting humans can be traced to animals or animal products. You can get a disease directly from an animal, or indirectly, through the environment.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert A78 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
083.0 Q fever
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About A78Overview

What is the ICD-10 code for q fever?

The ICD-10-CM code for q fever is A78. It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is A78 (Q fever) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report q fever on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does A78 group to?

When q fever is the principal diagnosis on an inpatient stay, it groups to MS-DRG 867, 868, 869, with relative weights from 0.7297 to 2.0932 depending on complications. Higher weights mean higher Medicare reimbursement.

Is A78 a CC or MCC?

CMS lists A78 as a CC (complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 56 closely related codes in its exclusion list.

What is the ICD-9 equivalent of A78?

Under the General Equivalence Mappings, q fever converts to ICD-9-CM 083.0 (q fever). The mapping is a direct match.