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ICD-10-CM 2027 diagnosis code

B33.3Retrovirus infections, not elsewhere classified

✓ Billable / specific

B33.3 is a valid, billable ICD-10-CM code for retrovirus infections, not elsewhere classified. 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 Retrovirus infection.

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 B33.3

B33.3 is the ICD-10-CM diagnosis code for retrovirus infections, not elsewhere classified. It belongs to category B33 (other viral diseases, not elsewhere classified), 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 B33 (other viral diseases, not elsewhere classified), B33.3 is specifically for retrovirus infections, not elsewhere classified. Related codes cover epidemic myalgia (B33.0), Ross River disease (B33.1), viral carditis (B33.2), Hantavirus (cardio)-pulmonary syndrome [HPS] [HCPS] (B33.4) and other specified viral diseases (B33.8).

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 079.59 (other specified retrovirus).

Coding notes

Applicable toConditions and synonyms classified to this code
  • Retrovirus infection NOS

Notes that apply from higher levels

Instructions written at a parent level also apply to B33.3.

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

Alphabetic index entries

3 entries

Terms in the official ICD-10-CM index that lead to B33.3.

Codes whose notes reference B33.3

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 →
  • 079.59Other specified retrovirusapproximate

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 B33.3

Is B33.3 billable?

Yes. B33.3 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can B33.3 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict B33.3 as a principal diagnosis.

Is B33.3 a CC or MCC?

No. B33.3 is neither a CC nor an MCC under MS-DRG v44.0.

What DRG does B33.3 group to?

B33.3 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 B33.3?

The CMS General Equivalence Mappings map B33.3 to ICD-9-CM 079.59.