2027 ICD-10-CM Diagnosis Code A78Q fever

ICD-10-CM Codes›A00–B99›A75-A79›A78

ICD-10-CM A78
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

A78 is a billable ICD-10-CM diagnosis code for q fever. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) 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

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to A78: its own notes plus those printed at Chapter 1. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • diseases generally recognized as communicable or transmissible

Applicable To

Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.

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

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • carrier or suspected carrier of infectious disease (Z22.-)
  • certain localized infections - see body system-related chapters
  • infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
  • infectious and parasitic diseases specific to the perinatal period (P35-P39)
  • influenza and other acute respiratory infections (J00-J22)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • code to identify resistance to antimicrobial drugs (Z16.-)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name A78, its category, or a range that includes it.

Code First 2

These codes say to code first a condition named in the note, and A78 is one of the conditions named.

  • I39 Endocarditis and heart valve disorders in diseases classified elsewhere
    Q fever (A78)
  • J17 Pneumonia in diseases classified elsewhere
    Q fever (A78)

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).

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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

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, 2026 through September 30, 2027.

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, 2026 through September 30, 2027.

What MS-DRG does A78 group to?

When q fever is the principal diagnosis on an inpatient stay, it groups to MS-DRG 867, 869, 868, with relative weights from 0.6784 to 2.1855 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 2027. 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.