2026 ICD-10-CM Diagnosis Code A08.31Calicivirus enteritis

ICD-10-CM Codes›A00–B99›A00-A09›A08

ICD-10-CM A08.31
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A08.31 is a billable ICD-10-CM diagnosis code for calicivirus enteritis. 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. 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 92 closely related codes. 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
A08.31
Billable Status
Yes — Valid for Submission
Code Describes
Calicivirus enteritis
Short Description
Calicivirus enteritis
Same as the full description in the CMS dataset.
Parent Code
A08.3
Other viral enteritis

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA00-A09Intestinal infectious diseases
CategoryA08Viral and other specified intestinal infections
This CodeA08.31Calicivirus enteritis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Calicivirus gastroenteritis
  • Disease caused by Calicivirus
  • Food poisoning caused by Norovirus
  • Infection caused by Norovirus
  • Inflammation of small intestine caused by Calicivirus
  • Viral food poisoning
  • Viral gastroenteritis caused by Sapovirus

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 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 A08.31 to ICD-9-CMHistory

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

ICD-9-CM
008.65 Enteritis d/t calicivirs
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 A08.31Overview

What is the ICD-10 code for calicivirus enteritis?

The ICD-10-CM code for calicivirus enteritis is A08.31 (sometimes written as A0831). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is A08.31 (Other viral enteritis) a billable code?

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

What MS-DRG does A08.31 group to?

When calicivirus enteritis 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.

Is A08.31 a CC or MCC?

CMS lists A08.31 as a CC (complication or comorbidity) for FY 2026. 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 92 closely related codes in its exclusion list.

What is the ICD-9 equivalent of A08.31?

Under the General Equivalence Mappings, calicivirus enteritis converts to ICD-9-CM 008.65 (enteritis d/t calicivirs). The mapping is a direct match.