ICD-10-CM 2027 diagnosis code
A77.0Spotted fever due to Rickettsia rickettsii
A77.0 is a valid, billable ICD-10-CM code for spotted fever due to rickettsia rickettsii. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.
Looking up by condition? See ICD-10 code for Rocky Mountain fever, ICD-10 code for Sao Paulo fever or typhus.
Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data
About A77.0
A77.0 is the ICD-10-CM diagnosis code for spotted fever due to Rickettsia rickettsii. It belongs to category A77 (spotted fever [tick-borne rickettsioses]), block A75-A79 (rickettsioses) and chapter 1 (certain infectious and parasitic diseases). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.
Within A77 (spotted fever [tick-borne rickettsioses]), A77.0 is specifically for spotted fever due to Rickettsia rickettsii. Related codes cover spotted fever due to Rickettsia conorii (A77.1), spotted fever due to Rickettsia siberica (A77.2), spotted fever due to Rickettsia australis (A77.3), ehrlichiosis (A77.4), other spotted fevers (A77.8) and spotted fever, unspecified (A77.9).
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.
Before ICD-10, this condition was coded in ICD-9-CM as 082.0 (spotted fevers).
Coding notes
- Rocky Mountain spotted fever
- Sao Paulo fever
Notes that apply from higher levels
Instructions written at a parent level also apply to A77.0.
Broader instructions also apply from Chapter 1: Certain infectious and parasitic diseases.
Alphabetic index entries
15 entriesTerms in the official ICD-10-CM index that lead to A77.0.
- Fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor) › American › spotted
- Fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor) › Bullis
- Fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor) › Lone Star
- Fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor) › mountain › meaning Rocky Mountain spotted fever
- Fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor) › Rocky Mountain spotted
- Fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor) › Sao Paulo
- Fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor) › spotted › American
- Fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor) › spotted › Brazilian
- Fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor) › spotted › Colombian
- Fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor) › spotted › due to Rickettsia › rickettsii
- Fever (inanition) (of unknown origin) (persistent) (with chills) (with rigor) › spotted › Rocky Mountain
- Lone Star fever
- Rocky Mountain (spotted) fever
- Sao Paulo fever or typhus
- Typhus (fever) › Sao Paulo
MS-DRG v44.0 grouping
All DRGs →Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.
MDC 18 · Infectious and Parasitic Diseases, Systemic or Unspecified Sites
ICD-9-CM equivalent
Converter →- 082.0Spotted feversapproximate
From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.
Code history
- 2016
- 2017
- 2018
- 2019
- 2020
- 2021
- 2022
- 2023
- 2024
- 2025
- 2026
- 2027
- FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
- No changes since FY2016.
Common questions about A77.0
Is A77.0 billable?
- Yes. A77.0 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can A77.0 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict A77.0 as a principal diagnosis.
Is A77.0 a CC or MCC?
- A77.0 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.
What DRG does A77.0 group to?
- A77.0 is used in the MS-DRG v44.0 logic for MS-DRG 867 (Other Infectious and Parasitic Diseases Diagnoses with MCC), MS-DRG 868 (Other Infectious and Parasitic Diseases Diagnoses with CC) and MS-DRG 869 (Other Infectious and Parasitic Diseases Diagnoses without CC/MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.
What is the ICD-9 code for A77.0?
- The CMS General Equivalence Mappings map A77.0 to ICD-9-CM 082.0.