A83 – Mosquito-borne viral encephalitis

ICD-10-CM 2027 diagnosis code · Viral and prion infections of the central nervous system

Non-billable header

ICD-10-CM code A83

Code: A83 (claims format: A83)
Description: Mosquito-borne viral encephalitis
Billable: No – use a more specific code below
Valid for: Dates of service October 1, 2026 – September 30, 2027 (FY2027)
Chapter: 1. Certain infectious and parasitic diseases (A00-B99)
Block: A80-A89 Viral and prion infections of the central nervous system

Billable codes under A83

A83 is a header code and cannot be used on claims. Choose the most specific code:

A83.0 – Japanese encephalitisBillable
A83.1 – Western equine encephalitisBillable
A83.2 – Eastern equine encephalitisBillable
A83.3 – St Louis encephalitisBillable
A83.4 – Australian encephalitisBillable
A83.5 – California encephalitisBillable
A83.6 – Rocio virus diseaseBillable
A83.8 – Other mosquito-borne viral encephalitisBillable
A83.9 – Mosquito-borne viral encephalitis, unspecifiedBillable

Notes for A83

Includes:

mosquito-borne viral meningoencephalitis

Excludes2 (not included here):

Venezuelan equine encephalitis (A92.2)
West Nile fever (A92.3-)
West Nile virus (A92.3-)

Notes inherited from parent codes

Instructional notes at a category or block level apply to every code below it.

Block A80-A89

Excludes1 (not coded here):

postpolio syndrome (G14)
sequelae of poliomyelitis (B91)
sequelae of viral encephalitis (B94.1)

Frequently asked questions

What is ICD-10 code A83?

A83 is the ICD-10-CM code for mosquito-borne viral encephalitis, in the block A80-A89 (Viral and prion infections of the central nervous system).

Is A83 a billable code?

No. A83 is a header code with more specific child codes; report one of the billable codes listed above.

Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.