ICD-10-CM 2027
ICD-10 code for Eastern equine encephalitis
From the official ICD-10-CM alphabetic index entry “Encephalitis (chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute) › Eastern equine”. Page updated September 29, 2026.
About coding Eastern equine encephalitis
The ICD-10-CM code for Eastern equine encephalitis is A83.2 (Eastern equine encephalitis).
Within A83 (mosquito-borne viral encephalitis), A83.2 is specifically for Eastern equine encephalitis. Related codes cover Japanese encephalitis (A83.0), Western equine encephalitis (A83.1), St Louis encephalitis (A83.3), Australian encephalitis (A83.4), California encephalitis (A83.5), Rocio virus disease (A83.6), other mosquito-borne viral encephalitis (A83.8) and unspecified (A83.9).
As a secondary diagnosis it is an MCC (major complication or comorbidity), which can move an inpatient stay into the highest-paying "with MCC" MS-DRG of its family, unless the principal diagnosis excludes it.
In MS-DRG v44.0, it is part of the grouping logic for DRG 023 (Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis with MCC or Antineoplastic Implant or Epilepsy with Neurostimulator, relative weight 5.7444), DRG 024 (Craniotomy with Major Device Implant or Acute Complex CNS Principal Diagnosis without MCC, relative weight 3.9708), DRG 097 (Non-Bacterial Infection of Nervous System Except Viral Meningitis with MCC, relative weight 3.8226), DRG 098 (Non-Bacterial Infection of Nervous System Except Viral Meningitis with CC, relative weight 2.2706) and DRG 099 (Non-Bacterial Infection of Nervous System Except Viral Meningitis without CC/MCC, relative weight 1.5256), in MDC 01 (Diseases and Disorders of the Nervous System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
Common questions about Eastern equine encephalitis ICD-10 codes
What is the ICD-10 code for Eastern equine encephalitis?
- A83.2 — Eastern equine encephalitis.
Is A83.2 billable?
- Yes. A83.2 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can A83.2 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict A83.2 as a principal diagnosis.
Is A83.2 a CC or MCC?
- A83.2 is an MCC (major complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.