FY2027
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Excludes1 pair

A49- vs A79.9

A49 and A79.9 are not coded together. ICD-10-CM declares them mutually exclusive with an Excludes1 note — the two conditions are not expected to occur together, so exactly one of them is normally correct for a given encounter. The Official Guidelines carve out one exception: if the two conditions are clearly unrelated to each other, both may be reported.

The official note, declared on A49
rickettsial infection NOS (A79.9)
A49

Bacterial infection of unspecified site

Not billable
Chapter 1
Certain infectious and parasitic diseases
Section
A30-A49
A79.9

Rickettsiosis, unspecified

BillableUnspecified
Chapter 1
Certain infectious and parasitic diseases
Section
A75-A79
Use when the record says
  • Rickettsial infection NOS
Indexed under
  • Rickettsial disease
  • Rickettsiosis
  • Disease, diseased › rickettsial NOS
  • Infection, infected, infective › rickettsial NOS

Excludes1 is not always absolute: where two conditions covered by the note are genuinely unrelated, CMS guidance permits reporting both. Document the reasoning rather than assuming it. More on Excludes1 vs Excludes2 · FY2027