2026 ICD-10-CM Diagnosis Code A49.9Bacterial infection, unspecified

ICD-10-CM Codes›A00–B99›A30-A49›A49

ICD-10-CM A49.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A49.9 is a billable ICD-10-CM diagnosis code for bacterial infection, 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
A49.9
Billable Status
Yes — Valid for Submission
Code Describes
Bacterial infection, unspecified
Short Description
Bacterial infection, unspecified
Same as the full description in the CMS dataset.
Parent Code
A49
Bacterial infection of unspecified site

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA30-A49Other bacterial diseases
CategoryA49Bacterial infection of unspecified site
This CodeA49.9Bacterial infection, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Abscess of aortic valve
  • Abscess of mitral valve
  • Abscess of pulmonary valve
  • Acne with gram negative folliculitis
  • Acute bacterial otitis externa
  • Acute bacterial tubulointerstitial nephritis
  • Acute infectious tubulointerstitial nephritis
  • Acute infective otitis externa
  • Acute pyelonephritis
  • Acute pyelonephritis caused by bacterium
  • Acute tubulointerstitial nephritis
  • Angular cheilitis
  • Angular cheilitis due to bacterial infection
  • Autoinflammatory syndrome with pyogenic bacterial infection and amylopectinosis
  • Autoinflammatory syndrome with pyogenic bacterial infection and amylopectinosis due to HOIP deficiency
  • Bacterial abscess of aortic valve
  • Bacterial abscess of mitral valve
  • Bacterial abscess of pulmonary valve
  • Bacterial cellulitis
  • Bacterial corneal ulcer
  • Bacterial encephalitis
  • Bacterial endophthalmitis
  • Bacterial esophagitis
  • Bacterial folliculitis
  • Bacterial genital infection
  • Bacterial infection associated with peritoneal dialysis catheter
  • Bacterial infection due to human immunodeficiency virus infection
  • Bacterial infection of central nervous system
  • Bacterial infection of skin
  • Bacterial infectious disease
  • Bacterial musculoskeletal infection
  • Bacterial nephritis
  • Bacterial oral infection
  • Bacterial osteomyelitis
  • Bacterial otitis media
  • Bacterial respiratory infection
  • Bacterial sinusitis
  • Bacterial tenosynovitis
  • Bacterial tonsillitis
  • Bacterial upper respiratory infection
  • Bacterial urogenital infection
  • Beta lactam resistant bacterial infection
  • Botryomycosis
  • Cutaneous reaction caused by bacterial toxin
  • Disease caused by Gram-negative bacteria
  • Erythema nodosum due to bacterial infection
  • Gram-negative bacterial cellulitis
  • Gram-negative folliculitis
  • Herpes zoster with secondary bacterial infection
  • Infection associated with peritoneal dialysis catheter
  • Infection caused by aminoglycoside resistant bacteria
  • Infection caused by anaerobic bacteria
  • Infection caused by antimicrobial resistant bacteria
  • Infection caused by carbapenem resistant bacteria
  • Infection caused by multi drug resistant bacteria
  • Infection caused by quinolone and fluoroquinolone resistant bacteria
  • Invasive bacterial infectious disease
  • Moderate cavitated lesion limited to outer half of dentin
  • Neonatal hyperbilirubinemia due to bacterial infection
  • Neuropathy caused by bacterial toxin
  • Non-pyogenic bacterial infection of skin
  • Peripheral neuropathy caused by toxin
  • Pleural effusion caused by bacteria
  • Pyogenic bacterial infection due to MyD88 deficiency
  • Recurrent bacterial infection
  • Superficial bacterial infection of skin
  • Toxic polyneuropathy

Tabular List NotesGuidance

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

Type 1 Excludes

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.

    • Arthritis, arthritic(acute) (chronic) (nonpyogenic) (subacute)
      • in (due to)
        • bacterial disease
    • Disease, diseased
      • bacterial
    • Infection, infected, infective(opportunistic)
      • Bacillus
    • Infection, infected, infective(opportunistic)
      • bacterial NOS
    • Infection, infected, infective(opportunistic)
      • gram-negative bacilli NOS

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

  • Bacterial Esophagitis

    an acute bacterial infection that affects the esophagus. symptoms include severe pain on swallowing and retrosternal pain. endoscopic examination reveals esophageal mucosal ulcerations and pseudomembranous formations.

  • Acute Pyelonephritis

    sudden onset pyelonephritis.

  • Toxic Polyneuropathy

    polyneuropathy that is caused by exposure to toxins.

  • Bacterial Endophthalmitis

    endophthalmitis caused by bacterial infection of the vitreous or aqueous humors.

  • Chronic Toxic Polyneuropathy

    neuropathy affecting multiple nerves that is caused by prolonged exposure to toxic substances.

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 A49.9 to ICD-9-CMHistory

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

ICD-9-CM
041.9 Bacterial infection NOS
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 A49.9Overview

Is A49.9 (Bacterial infection of unspecified site) a billable code?

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

What MS-DRG does A49.9 group to?

When bacterial infection, 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 A49.9?

Under the General Equivalence Mappings, bacterial infection, unspecified converts to ICD-9-CM 041.9 (bacterial infection NOS). 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.