A83.4
BillableAustralian encephalitis
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is A83.4 an HCC code?
No. A83.4 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
A83.4 is the ICD-10-CM diagnosis code for australian encephalitis. Australian encephalitis is a viral infection that causes inflammation of the brain, transmitted through mosquito bites in Australia and nearby regions. It can cause fever, headache, confusion, and in severe cases, neurological complications. A83.4 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering viral and prion infections of the central nervous system (a80-a89).
A83.4 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
Verify the documentation specifies Australian encephalitis (also called Murray Valley encephalitis) rather than other forms of encephalitis, as this code is specific to this geographic and viral etiology.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for A83.4 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify the documentation specifies Australian encephalitis (also called Murray Valley encephalitis) rather than other forms of encephalitis, as this code is specific to this geographic and viral etiology
- •Look for associated complications such as seizures, altered mental status, or neurological sequelae that may require additional codes to fully capture the clinical picture