2027 ICD-10-CM Diagnosis Code A99Unspecified viral hemorrhagic fever

ICD-10-CM Codes›A00–B99›A90-A99›A99

ICD-10-CM A99
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

A99 is a billable ICD-10-CM diagnosis code for unspecified viral 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 viral hemorrhagic fever. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Viral infection.

Code Identity

ICD-10-CM Code
A99
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified viral hemorrhagic fever
Short Description
Unspecified viral 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
CategoryA99Unspecified viral hemorrhagic fever
This CodeA99Unspecified viral hemorrhagic fever

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Viral hemorrhagic fever

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to A99: 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.

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

Patient EducationClinical

Hemorrhagic Fevers

Viral hemorrhagic fevers (VHFs) are a group of illnesses caused by four families of viruses. These include the Ebola and Marburg, Lassa fever, and yellow fever viruses. VHFs have common features: they affect many organs, they damage the blood vessels, and they affect the body's ability to regulate itself.

Read the full article at MedlinePlus

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

Convert A99 to ICD-9-CMHistory

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

ICD-9-CM
065.9 Arthropod hem fever NOS
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 A99Overview

What is the ICD-10 code for unspecified viral hemorrhagic fever?

The ICD-10-CM code for unspecified viral hemorrhagic fever is A99. It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is A99 (Unspecified viral hemorrhagic fever) a billable code?

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

What MS-DRG does A99 group to?

When unspecified viral 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 A99 a CC or MCC?

CMS lists A99 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 A99?

Under the General Equivalence Mappings, unspecified viral hemorrhagic fever converts to ICD-9-CM 065.9 (arthropod hem fever NOS). The mapping is approximate, so confirm the match fits the documentation.