ICD-10-CM 2027 diagnosis code

B01.1Varicella encephalitis, myelitis and encephalomyelitis

Not billable — use a more specific code

B01.1 is a header code, so it can't be reported by itself. Choose one of the 2 more specific codes beneath it.

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 B01.1

B01.1 is the ICD-10-CM diagnosis code for varicella encephalitis, myelitis and encephalomyelitis. It belongs to category B01 (varicella [chickenpox]), block B00-B09 (viral infections characterized by skin and mucous membrane lesions) and chapter 1 (certain infectious and parasitic diseases). It is a header code, so it can't be reported by itself; one of its 2 subcodes must be used instead.

Within B01 (varicella [chickenpox]), B01.1 is specifically for varicella encephalitis, myelitis and encephalomyelitis. Related codes cover meningitis (B01.0), pneumonia (B01.2), with other complications (B01.8) and without complication (B01.9).

To report this condition, pick the subcode that matches the documentation: B01.11 (encephalomyelitis) and B01.12 (myelitis).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Specific codes under B01.1

Coding notes

Applicable toConditions and synonyms classified to this code

Postchickenpox encephalitis, myelitis and encephalomyelitis

Notes that apply from higher levels

Instructions written at a parent level also apply to B01.1.

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

Codes whose notes reference B01.1

G04.01Excludes1
G05Excludes1

Code history

2016
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2025
2026
2027

FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
No changes since FY2016.

Common questions about B01.1

Is B01.1 billable?: No. B01.1 is a header code. Report one of its more specific subcodes instead.