ICD-10-CM 2027
ICD-10 code for bacterial disease
From the official ICD-10-CM alphabetic index entry “Disease, diseased › bacterial”. Page updated September 29, 2026.
About coding bacterial disease
The ICD-10-CM code for bacterial disease is A49.9 (Bacterial infection, unspecified). The official index lists 3 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on A49.9.
Within A49, choose A49.9 (Bacterial infection, unspecified) only when documentation doesn't support a more specific option: staphylococcal infection, unspecified site (A49.0), streptococcal infection, unspecified site (A49.1), hemophilus influenzae infection, unspecified site (A49.2), mycoplasma infection, unspecified site (A49.3) and other bacterial infections of unspecified site (A49.8).
Don't report A49.9 together with the conditions in its Excludes1 note: bacteremia NOS (R78.81).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
More specific bacterial disease codes (official index)
Don't confuse with (Excludes1 for A49.9)
- bacteremia NOS (R78.81)
Common questions about bacterial disease ICD-10 codes
What is the ICD-10 code for bacterial disease?
- A49.9 — Bacterial infection, unspecified. More specific codes apply when the documentation supports them: A48.8, A28.9, A28.8.
What is the ICD-10 code for zoonotic bacterial disease?
- A28.9 — Zoonotic bacterial disease, unspecified.
Is A49.9 billable?
- Yes. A49.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can A49.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict A49.9 as a principal diagnosis.
Is A49.9 a CC or MCC?
- No. A49.9 is neither a CC nor an MCC under MS-DRG v44.0.