2026 ICD-10-CM Diagnosis Code B10.01Human herpesvirus 6 encephalitis

ICD-10-CM Codes›A00–B99›B10›B10

ICD-10-CM B10.01
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

B10.01 is a billable ICD-10-CM diagnosis code for human herpesvirus 6 encephalitis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 974 through 976. Coders also document this condition as encephalitis caused by human herpesvirus 6 infection. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Encephalitis and Viral infection.

Code Identity

ICD-10-CM Code
B10.01
Billable Status
Yes — Valid for Submission
Code Describes
Human herpesvirus 6 encephalitis
Short Description
Human herpesvirus 6 encephalitis
Same as the full description in the CMS dataset.
Parent Code
B10.0
Other human herpesvirus encephalitis

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionB10Other human herpesviruses
CategoryB10Other human herpesviruses
This CodeB10.01Human herpesvirus 6 encephalitis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Encephalitis caused by human herpesvirus 6 infection
  • Infection by human herpesvirus 6
  • Infection caused by Roseolovirus

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.

    • Encephalitis(chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
      • herpesviral
        • due to herpesvirus 6
    • Encephalitis(chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
      • in (due to)
        • herpes (simplex) virus
          • due to herpesvirus 6
    • Herpes, herpesvirus, herpetic
      • encephalitis
        • due to herpesvirus 6
    • Herpes, herpesvirus, herpetic
      • human
        • 6
          • encephalitis
    • Meningoencephalitis
      • herpesviral, herpetic
        • due to herpesvirus 6
    • Meningoencephalitis
      • in (due to)
        • herpes
          • due to herpesvirus 6

Clinical ClassificationClinical

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

CCSR NVS002
Encephalitis
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR INF008
Viral infection
Default principal diagnosis: inpatient No · outpatient No

Patient EducationClinical

Encephalitis

Encephalitis is inflammation (swelling) of the brain. It can happen when an infection or medical condition that affects the brain activates your immune system. The inflammation can cause a wide range of symptoms. In extreme cases, it can lead to brain damage, stroke, or even death.

The full article covers:

  • What is encephalitis?
  • What causes encephalitis?
  • Who is more likely to get encephalitis?
  • What are the symptoms of encephalitis?
  • How is encephalitis diagnosed?
  • What are the treatments for encephalitis?
  • Can encephalitis be prevented?

Read the full article at MedlinePlus

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

Convert B10.01 to ICD-9-CMHistory

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

ICD-9-CM
058.21 Human herpesvir 6 enceph
Exact Match The mapping is direct, with no qualifiers.

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 B10.01Overview

Is B10.01 (Other human herpesvirus encephalitis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report human herpesvirus 6 encephalitis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does B10.01 group to?

When human herpesvirus 6 encephalitis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 974, 975, 976, with relative weights from 0.8945 to 2.8860 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of B10.01?

Under the General Equivalence Mappings, human herpesvirus 6 encephalitis converts to ICD-9-CM 058.21 (human herpesvir 6 enceph). The mapping is a direct match.

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.