Tick-borne viral encephalitis (A84) ICD-10-CM
The A84 code range covers tick-borne viral encephalitis with 7 ICD-10-CM diagnosis codes. 5 of them are billable and valid for claim submission in fiscal year 2026, and the category headers group them but cannot themselves be billed.
Includes
This note appears immediately under a three character code title to further define, or give examples of, the content of the category.
- tick-borne viral meningoencephalitis
Codes in the A84 Range 7 codes · 5 billable
- A84 Tick-borne viral encephalitisNon-billable
- A84.0 Far Eastern tick-borne encephalitis [Russian spring-summer encephalitis]
- A84.1 Central European tick-borne encephalitis
- A84.8 Other tick-borne viral encephalitisNon-billable
- A84.81 Powassan virus disease
- A84.89 Other tick-borne viral encephalitis
- A84.9 Tick-borne viral encephalitis, unspecified
About the A84 Code Range
ICD-10 code A84 identifies infections classified as tick-borne viral encephalitis, a group of viral diseases affecting the brain caused by viruses transmitted through tick bites.
This section covers several specific forms of tick-borne viral encephalitis. A84.0 is used for Far Eastern tick-borne encephalitis, also called Russian spring-summer encephalitis, caused by the Far Eastern tick-borne encephalitis virus. A84.1 refers to Central European tick-borne encephalitis, linked to the European subtype of the virus. Codes like A84.8 and A84.89 classify other types, including illnesses from viruses such as louping ill and Siberian tick-borne encephalitis virus. A84.81 specifically defines Powassan virus disease, which can present as invasive or neuroinvasive encephalitis. When the exact virus is not identified, A84.9 is applied as unspecified tick-borne viral encephalitis. Using these codes correctly helps pinpoint the cause of viral encephalitis related to tick exposure for accurate diagnosis and reporting.
Questions About This Page
How many billable codes are in the A84 range?
Of the 7 codes in this range, 5 are billable and valid for claim submission from October 1, 2025 through September 30, 2026. Category header codes group them but cannot be reported on claims.
What does the A84 range classify?
The range classifies tick-borne viral encephalitis. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2026 ICD-10-CM Tabular List and order file, effective October 1, 2025 through September 30, 2026.
