2026 ICD-10-CM Diagnosis Code A04.1Enterotoxigenic Escherichia coli infection

ICD-10-CM Codes›A00–B99›A00-A09›A04

ICD-10-CM A04.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A04.1 is a billable ICD-10-CM diagnosis code for enterotoxigenic Escherichia coli infection. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 371 through 373. Coders also document this condition as colitis caused by enterotoxigenic Escherichia coli. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections and Intestinal infection.

Code Identity

ICD-10-CM Code
A04.1
Billable Status
Yes — Valid for Submission
Code Describes
Enterotoxigenic Escherichia coli infection
Short Description
Enterotoxigenic Escherichia coli infection
Same as the full description in the CMS dataset.
Parent Code
A04
Other bacterial intestinal infections

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA00-A09Intestinal infectious diseases
CategoryA04Other bacterial intestinal infections
This CodeA04.1Enterotoxigenic Escherichia coli infection

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Colitis caused by enterotoxigenic Escherichia coli
  • Enteritis of small intestine caused by Escherichia coli
  • Enterotoxigenic Escherichia coli enteritis of intestine
  • Enterotoxigenic Escherichia coli enteritis of small intestine
  • Enterotoxigenic Escherichia coli gastrointestinal tract infection
  • Escherichia coli colitis
  • Traveler's diarrhea

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.

    • Diarrhea, diarrheal(disease) (infantile) (inflammatory)
      • due to
        • Escherichia coli
          • enterotoxigenic
    • Enteritis(acute) (diarrheal) (hemorrhagic) (noninfective)
      • infectious NOS
        • due to
          • Escherichia coli
            • enterotoxigenic

Clinical ClassificationClinical

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

CCSR INF003
Bacterial infections
Default principal diagnosis: inpatient No · outpatient No
CCSR DIG001
Intestinal infection
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

E. Coli Infections

E. coli is the name of a type of bacteria that lives in your intestines. Most types of E. coli are harmless. However, some types can make you sick and cause diarrhea. One type causes travelers' diarrhea. The worst type of E. coli causes bloody diarrhea, and can sometimes cause kidney failure and even death.

Read the full article at MedlinePlus

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

Convert A04.1 to ICD-9-CMHistory

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

ICD-9-CM
008.02 Int inf e coli entrtoxgn
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 A04.1Overview

Is A04.1 (Other bacterial intestinal infections) a billable code?

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

What MS-DRG does A04.1 group to?

When enterotoxigenic Escherichia coli infection is the principal diagnosis on an inpatient stay, it groups to MS-DRG 371, 372, 373, with relative weights from 0.7274 to 1.7731 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of A04.1?

Under the General Equivalence Mappings, enterotoxigenic Escherichia coli infection converts to ICD-9-CM 008.02 (int inf e coli entrtoxgn). 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.