2026 ICD-10-CM Diagnosis Code A27.9Leptospirosis, unspecified

ICD-10-CM Codes›A00–B99›A20-A28›A27

ICD-10-CM A27.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A27.9 is a billable ICD-10-CM diagnosis code for leptospirosis, unspecified. 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections.

Code Identity

ICD-10-CM Code
A27.9
Billable Status
Yes — Valid for Submission
Code Describes
Leptospirosis, unspecified
Short Description
Leptospirosis, unspecified
Same as the full description in the CMS dataset.
Parent Code
A27
Leptospirosis

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA20-A28Certain zoonotic bacterial diseases
CategoryA27Leptospirosis
This CodeA27.9Leptospirosis, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Anicteric leptospirosis
  • Encephalitis caused by Leptospira
  • Intracranial hemorrhage due to leptospirosis
  • Leptospira infection of the central nervous system
  • Leptospiral rash
  • Leptospirosis
  • Leptospirosis immune phase
  • Leptospirosis leptospiremic phase
  • Leptospirosis with cutaneous involvement
  • Miscarriage due to Leptospira
  • Non-pyogenic bacterial infection of skin
  • Pulmonary hemorrhage due to leptospirosis

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Fever(inanition) (of unknown origin) (persistent) (with chills) (with rigor)
      • mud
    • Fever(inanition) (of unknown origin) (persistent) (with chills) (with rigor)
      • swamp
    • Infection, infected, infective(opportunistic)
      • Leptospira interrogans
    • Leptospirosis

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

  • Leptospirosis

    infections with bacteria of the genus leptospira.

  • Weil Disease

    a severe form of leptospirosis, usually caused by leptospira interrogans serovar icterohaemorrhagiae and occasionally other serovars. it is transmitted to humans by the rat and is characterized by hemorrhagic and renal symptoms with accompanying jaundice.

  • Leptospira

    a genus of aerobic, helical spirochetes, some species of which are pathogenic, others free-living or saprophytic.

Patient EducationClinical

Bacterial Infections

Bacteria are tiny organisms (living things) that have only one cell. Under a microscope, they look like balls, rods, or spirals. They can be found almost everywhere on Earth. There are lots of bacteria in and on your body. In fact, your body has about 10 times more bacteria cells than human cells.

The full article covers:

  • What are bacteria?
  • How do bacterial infections spread?
  • What are the treatments for bacterial infections?
  • Can bacterial infections be prevented?

Read the full article at MedlinePlus

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

Convert A27.9 to ICD-9-CMHistory

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

ICD-9-CM
100.9 Leptospirosis NOS
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 A27.9Overview

Is A27.9 (Leptospirosis) a billable code?

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

What MS-DRG does A27.9 group to?

When leptospirosis, unspecified 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.

What is the ICD-9 equivalent of A27.9?

Under the General Equivalence Mappings, leptospirosis, unspecified converts to ICD-9-CM 100.9 (leptospirosis NOS). The mapping is a direct match.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.