ICD-10-CM 2027
ICD-10 code for Flexner's bacillus
From the official ICD-10-CM alphabetic index entry “Bacillus › Flexner's”. Page updated September 29, 2026.
About coding Flexner's bacillus
The ICD-10-CM code for Flexner's bacillus is A03.1 (Shigellosis due to Shigella flexneri).
Within A03 (shigellosis), A03.1 is specifically for shigellosis due to Shigella flexneri. Related codes cover due to Shigella dysenteriae (A03.0), due to Shigella boydii (A03.2), due to Shigella sonnei (A03.3), other shigellosis (A03.8) and unspecified (A03.9).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 371 (Major Gastrointestinal Disorders and Peritoneal Infections with MCC, relative weight 1.7089), DRG 372 (Major Gastrointestinal Disorders and Peritoneal Infections with CC, relative weight 0.9964) and DRG 373 (Major Gastrointestinal Disorders and Peritoneal Infections without CC/MCC, relative weight 0.6941), in MDC 06 (Diseases and Disorders of the Digestive System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
Common questions about Flexner's bacillus ICD-10 codes
What is the ICD-10 code for Flexner's bacillus?
- A03.1 — Shigellosis due to Shigella flexneri.
Is A03.1 billable?
- Yes. A03.1 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can A03.1 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict A03.1 as a principal diagnosis.
Is A03.1 a CC or MCC?
- No. A03.1 is neither a CC nor an MCC under MS-DRG v44.0.