2026 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 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A99 is a billable ICD-10-CM diagnosis code for unspecified viral hemorrhagic fever. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 865 through 866. 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
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

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Fever(inanition) (of unknown origin) (persistent) (with chills) (with rigor)
      • hemorrhagic (arthropod-borne) NOS
        • viral

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

  • Viral Hemorrhagic Fever

    a group of viral illnesses that are characterized by increased susceptibility to bleeding diatheses.

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 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About A99Overview

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, 2025 through September 30, 2026.

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 865, 866, with relative weights from 0.8696 to 1.4983 depending on complications. Higher weights mean higher Medicare reimbursement.

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.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.