2026 ICD-10-CM Diagnosis Code A08.11Acute gastroenteropathy due to Norwalk agent

ICD-10-CM Codes›A00–B99›A00-A09›A08

ICD-10-CM A08.11
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A08.11 is a billable ICD-10-CM diagnosis code for acute gastroenteropathy due to Norwalk agent. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 391 through 392. Coders also document this condition as calicivirus gastroenteritis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Intestinal infection and Viral infection.

Code Identity

ICD-10-CM Code
A08.11
Billable Status
Yes — Valid for Submission
Code Describes
Acute gastroenteropathy due to Norwalk agent
Short Description
Acute gastroenteropathy due to Norwalk agent
Same as the full description in the CMS dataset.
Parent Code
A08.1
Acute gastroenteropathy due to Norwalk agent and other small round viruses

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA00-A09Intestinal infectious diseases
CategoryA08Viral and other specified intestinal infections
This CodeA08.11Acute gastroenteropathy due to Norwalk agent

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Calicivirus gastroenteritis
  • Disease caused by Calicivirus
  • Epidemic vomiting syndrome
  • Infection caused by Norovirus
  • Inflammation of intestine caused by Norovirus
  • Norovirus GI and GII detected
  • Viral gastroenteritis caused by Norwalk-like agent

Tabular List NotesGuidance

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

Inclusion Terms

  • Acute gastroenteropathy due to Norovirus
  • Acute gastroenteropathy due to Norwalk-like agent

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.

    • Enteritis(acute) (diarrheal) (hemorrhagic) (noninfective)
      • norovirus
    • Gastroenteritis(acute) (chronic) (noninfectious)
      • viral NEC
        • acute infectious
          • type Norwalk
    • Gastroenteritis(acute) (chronic) (noninfectious)
      • viral NEC
        • Norwalk agent
    • Gastroenteropathy
      • acute, due to Norwalk agent
    • Gastroenteropathy
      • acute, due to Norovirus

Clinical ClassificationClinical

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

CCSR DIG001
Intestinal infection
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR INF008
Viral infection
Default principal diagnosis: inpatient No · outpatient No

Patient EducationClinical

Gastroenteritis

Gastroenteritis is an inflammation of the lining of the stomach and intestines. The main symptoms include vomiting and diarrhea. It is usually not serious in healthy people, but it can sometimes lead to dehydration or cause severe symptoms.

The full article covers:

  • What is gastroenteritis?
  • What causes gastroenteritis?
  • What are the symptoms of gastroenteritis?
  • How is gastroenteritis diagnosed?
  • What are the treatments for gastroenteritis?
  • Can gastroenteritis be prevented?

Read the full article at MedlinePlus

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

Convert A08.11 to ICD-9-CMHistory

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

ICD-9-CM
008.63 Int inf norwalk virus
Approximate The match is approximate rather than exact.

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 A08.11Overview

Is A08.11 a billable code?

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

What MS-DRG does A08.11 group to?

When acute gastroenteropathy due to Norwalk agent is the principal diagnosis on an inpatient stay, it groups to MS-DRG 391, 392, with relative weights from 0.7796 to 1.2683 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of A08.11?

Under the General Equivalence Mappings, acute gastroenteropathy due to Norwalk agent converts to ICD-9-CM 008.63 (int inf norwalk virus). The mapping is approximate, so confirm the match fits the documentation.

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.