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A83.1

A83.1: Western equine encephalitis

Billable / specific codeICD-10-CM

A83.1 is a billable, specific ICD-10-CM code for western equine encephalitis. It is valid for submission on a claim.

Check A83.1 with the rest of the claim: free scrubber

Excludes2 inherited from the categories above A83.1

Not part of this code, but both may be coded when both are present.

Written on A83: Mosquito-borne viral encephalitis

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

Risk adjustment

No CMS-HCC V28 category: this code does not change a RAF score.

Medicare coverage

A83.1 is named in 5 Medicare coverage policies: 5 listing it as supporting medical necessity. Which one applies depends on your Medicare contractor.

  • A56612Billing and Coding: CT of the Head
  • A56771Billing and Coding: Special Electroencephalography
  • A56773Billing and Coding: Neurophysiology Evoked Potentials (NEPs)
  • A57204Billing and Coding: MRI and CT Scans of the Head and Neck

Alphabetic index entries that lead here

  • Encephalitis›Western equine
  • Encephalitis›equine›Western
  • Encephalomyelitis›equine›Western
  • Encephalitis›viral, virus›arthropod-borne NEC›mosquito-borne›Western equine

Code history

Unchanged in every release from FY2024 to FY2027.

Other codes under A83

ICD-10-CMFY2027· effective October 1, 2026

Loaded directly from the CMS/NCHS ICD-10-CM public-domain release: see data sources and our editorial policy. If this page disagrees with the CMS tabular list, this page is wrong. Reference information for professional coders; not medical or billing advice.