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ICD-10-CM 2027 diagnosis code

B27.00Gammaherpesviral mononucleosis without complication

✓ Billable / specific

B27.00 is a valid, billable ICD-10-CM code for gammaherpesviral mononucleosis without complication. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Looking up by condition? See ICD-10 code for Gammaherpesviral mononucleosis.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About B27.00

B27.00 is the ICD-10-CM diagnosis code for Gammaherpesviral mononucleosis without complication. It belongs to category B27 (infectious mononucleosis), block B25-B34 (other viral diseases) and chapter 1 (certain infectious and parasitic diseases). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within B27.0, choose B27.00 (without complication) only when documentation doesn't support a more specific option: with polyneuropathy (B27.01), with meningitis (B27.02) and with other complications (B27.09).

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 865 (Viral Illness with MCC, relative weight 1.3485) and DRG 866 (Viral Illness without MCC, relative weight 0.8692), in MDC 18 (Infectious and Parasitic Diseases, Systemic or Unspecified Sites), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 075 (infectious mononucleosis).

Notes that apply from higher levels

Instructions written at a parent level also apply to B27.00.

› From B27 Infectious mononucleosis
Includes
  • glandular fever
  • monocytic angina
  • Pfeiffer's disease

Broader instructions also apply from Chapter 1: Certain infectious and parasitic diseases.

Alphabetic index entries

2 entries

Terms in the official ICD-10-CM index that lead to B27.00.

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

MDC 18 · Infectious and Parasitic Diseases, Systemic or Unspecified Sites

ICD-9-CM equivalent

Converter →
  • 075Infectious mononucleosisapproximate

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about B27.00

Is B27.00 billable?

Yes. B27.00 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can B27.00 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict B27.00 as a principal diagnosis.

Is B27.00 a CC or MCC?

No. B27.00 is neither a CC nor an MCC under MS-DRG v44.0.

What DRG does B27.00 group to?

B27.00 is used in the MS-DRG v44.0 logic for MS-DRG 865 (Viral Illness with MCC) and MS-DRG 866 (Viral Illness without MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for B27.00?

The CMS General Equivalence Mappings map B27.00 to ICD-9-CM 075.