B27.9 ICD-10-CA code: Infectious mononucleosis, unspecified
B27.9 is the ICD-10-CA code for “Infectious mononucleosis, unspecified” in CIHI’s FY 2026–2027 release, in effect from Apr 1, 2026.
Official description
B27.9Infectious mononucleosis, unspecified
Short description: Infectious mononucleosis unspecified
ICD-10-CA · Canada · Also written B279
Index terms
Entries in CIHI’s alphabetical index that lead to B27.9. Searching the index by the condition the note names is how coders reach this code.
- Fever, glandular
- Disease, diseased, kissing
- Mononucleosis, infectious NEC
- Angina (attack) (cardiac) (chest) (heart) (pectoris) (syndrome) (vasomotor), monocytic
Notes for B27.9
As CIHI prints them, with any note B27.9 takes from the headings above it.
Includes
- Glandular fevermonocytic anginaPfeiffer's diseaseFrom B27 Infectious mononucleosis
- Diseases generally recognized as communicable or transmissibleFrom Chapter 1: Certain infectious and parasitic diseases (A00-B99)
Use additional code
Add a code for this detail when the note documents it.
- Use additional code (U82-U84) to identify resistance to antimicrobial drugsFrom Chapter 1: Certain infectious and parasitic diseases (A00-B99)
Excludes
Conditions classified elsewhere.
- Carrier or suspected carrier of infectious disease (Z22.-)certain localized infections - see body system-related chaptersinfectious and parasitic diseases:• complicating pregnancy, childbirth and the puerperium [except obstetrical tetanus] (O98.-)• specific to the perinatal period [except tetanus neonatorum, whooping cough, congenital syphilis, perinatal gonococcal infection and perinatal human immunodeficiency virus [HIV] disease] (P35-P39)influenza and other acute respiratory infections (J00-J22)From Chapter 1: Certain infectious and parasitic diseases (A00-B99)
Where B27.9 sits
- 1ChapterChapter 1: Certain infectious and parasitic diseases (A00-B99)
- 2Block B25-B34Other viral diseases
- 3Category B27Infectious mononucleosis
- 4Valid code B27.9Infectious mononucleosis, unspecified
Source and release
- Data release
- ICD-10-CA · FY 2026–2027
- Effective date
- Apr 1, 2026
- Publisher
- CIHI
This page is built from the ICD-10-CA catalog that Vero Codes reads when it suggests codes: Canadian Institute for Health Information’s FY 2026–2027 release, imported from the publisher’s file and checked against it. The description, notes and structured data come from the same record.
Frequently asked questions
What does ICD-10-CA code B27.9 mean?
B27.9 is the ICD-10-CA code for “Infectious mononucleosis, unspecified” in CIHI’s ICD-10-CA FY 2026–2027 release.
Where is B27.9 in ICD-10-CA?
B27.9 sits under B27 Infectious mononucleosis, within B25-B34 Other viral diseases, within Chapter 1: Certain infectious and parasitic diseases (A00-B99).
What coding notes apply to B27.9?
ICD-10-CA lists Includes, Use additional code, Excludes notes for B27.9, including those from the headings it sits under. They are listed on this page with where each one comes from.
Which ICD-10-CA release does this page use?
It uses CIHI’s FY 2026–2027 release, in effect from Apr 1, 2026 to Mar 31, 2027. It is a reference: confirm the code against the current list and the payer’s rules before you submit it.