B03
Smallpox
B03 is a billable ICD-10-CM diagnosis code for smallpox. It is part of the FY2027 code set, effective October 1, 2026. The Alphabetic Index lists it under 4 entries. Its coding notes include a Use additional code instruction and 5 Excludes2 entries.
Use additional code
Add the listed code as a secondary code, if known.
Excludes2
Not included here. Both codes may be reported if the patient has both conditions.
Also from chapter/block level (5 notes)
- carrier or suspected carrier of infectious disease (Z22.-)
- certain localized infections - see body system-related chapters
- infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
- infectious and parasitic diseases specific to the perinatal period (P35-P39)
- influenza and other acute respiratory infections (J00-J22)
Care settings
How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.
Hospital CC
Counts as a complication or comorbidity (CC) when reported as a secondary diagnosis on an inpatient claim. It does not count when the principal diagnosis is one of the 13 codes in its exclusion list. Some MS-DRGs also ignore a CC or MCC that defines the DRG.
Source: CMS MS-DRG Definitions Manual v44, effective October 1, 2026, Appendix CIncludes
Further defines or gives examples of the content of the category.
Also from chapter/block level (1 note)
- diseases generally recognized as communicable or transmissible
Notes
- In 1980 the 33rd World Health Assembly declared that smallpox had been eradicated.
- The classification is maintained for surveillance purposes.
Alphabetic Index terms
Terms the official Alphabetic Index lists for this code. 4 entries