ICD-10-CM 2027 diagnosis code

A84Tick-borne viral encephalitis

Not billable — use a more specific code

A84 is a header code, so it can't be reported by itself. Choose one of the 4 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 A84

A84 is the ICD-10-CM diagnosis code for tick-borne viral encephalitis. It belongs to block A80-A89 (viral and prion infections of the central nervous system) and chapter 1 (certain infectious and parasitic diseases). It is a header code, so it can't be reported by itself; one of its 4 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: A84.0 (encephalitis]), A84.1 (encephalitis), A84.8 (encephalitis) and A84.9 (unspecified).

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 A84

Coding notes

IncludesFurther defines the content of the category

tick-borne viral meningoencephalitis

Notes that apply from higher levels

Instructions written at a parent level also apply to A84.

Broader instructions also apply from A80-A89 Viral and prion infections of the central nervous system and Chapter 1: Certain infectious and parasitic diseases.

Code history

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2027

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

Common questions about A84

Is A84 billable?: No. A84 is a header code. Report one of its more specific subcodes instead.