2027 ICD-10-CM Diagnosis Code A91Dengue hemorrhagic fever

ICD-10-CM Codes›A00–B99›A90-A99›A91

ICD-10-CM A91
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

A91 is a billable ICD-10-CM diagnosis code for dengue hemorrhagic fever. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 865 through 866. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 23 closely related codes. Coders also document this condition as dengue. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Viral infection.

Code Identity

ICD-10-CM Code
A91
Billable Status
Yes — Valid for Submission
Code Describes
Dengue hemorrhagic fever
Short Description
Dengue hemorrhagic fever
Same as the full description in the CMS dataset.
Chapter
A90-A99
Arthropod-borne viral fevers and viral hemorrhagic fevers

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA90-A99Arthropod-borne viral fevers and viral hemorrhagic fevers
CategoryA91Dengue hemorrhagic fever
This CodeA91Dengue hemorrhagic fever

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Dengue
  • Dengue hemorrhagic fever
  • Dengue hemorrhagic fever, grade I
  • Dengue hemorrhagic fever, grade II
  • Dengue hemorrhagic fever, grade III
  • Dengue hemorrhagic fever, grade IV
  • Dengue shock syndrome

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to A91: its own notes plus those printed at Chapter 1. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • diseases generally recognized as communicable or transmissible

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • 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)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • code to identify resistance to antimicrobial drugs (Z16.-)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name A91, its category, or a range that includes it.

Excludes1 2

These codes carry an Excludes1 note naming A91: they are not reported together with it, unless the two conditions are unrelated.

  • A90 Dengue fever [classical dengue]
    dengue hemorrhagic fever (A91)
  • A98 Other viral hemorrhagic fevers, not elsewhere classified
    dengue hemorrhagic fever (A91)

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INF008
Viral infection
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Severe Dengue

    a virulent form of dengue characterized by thrombocytopenia and an increase in vascular permeability (grades i and ii) and distinguished by a positive pain test (e.g., tourniquet pain test). when accompanied by shock (grades iii and iv), it is called dengue shock syndrome.

Patient EducationClinical

Dengue

Dengue is a viral infection. It can be caused by four related viruses. You can get it if an infected mosquito bites you. It is common in warm, wet areas of the world. Although rare, it can be found in some parts of the United States. Outbreaks are more common during rainy seasons.

The full article covers:

  • What is dengue?
  • How does dengue spread?
  • What are the symptoms of dengue and severe dengue?
  • How is dengue diagnosed?
  • What are the treatments for dengue?
  • Can dengue be prevented?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert A91 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
065.4 Mosquito-borne hem fever
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About A91Overview

What is the ICD-10 code for dengue hemorrhagic fever?

The ICD-10-CM code for dengue hemorrhagic fever is A91. It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is A91 (Dengue hemorrhagic fever) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report dengue hemorrhagic fever on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does A91 group to?

When dengue hemorrhagic fever is the principal diagnosis on an inpatient stay, it groups to MS-DRG 866, 865, with relative weights from 0.8691 to 1.3153 depending on complications. Higher weights mean higher Medicare reimbursement.

Is A91 a CC or MCC?

CMS lists A91 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 23 closely related codes in its exclusion list.

What is the ICD-9 equivalent of A91?

Under the General Equivalence Mappings, dengue hemorrhagic fever converts to ICD-9-CM 065.4 (mosquito-borne hem fever). The mapping is approximate, so confirm the match fits the documentation.