ICD-10-CM Code A83.1

Western equine encephalitis

Version 2020 Billable Code

Valid for Submission

A83.1 is a billable code used to specify a medical diagnosis of western equine encephalitis. The code is valid for the year 2020 for the submission of HIPAA-covered transactions. The ICD-10-CM code A83.1 might also be used to specify conditions or terms like neuroinvasive western equine encephalitis virus infection or non-neuroinvasive western equine encephalitis virus infection or western equine encephalitis.

Short Description:Western equine encephalitis
Long Description:Western equine encephalitis

Index to Diseases and Injuries

The Index to Diseases and Injuries is an alphabetical listing of medical terms, with each term mapped to one or more ICD-10 code(s). The following references for the code A83.1 are found in the index:


The following clinical terms are approximate synonyms or lay terms that might be used to identify the correct diagnosis code:

  • Neuroinvasive Western equine encephalitis virus infection
  • Non-neuroinvasive Western equine encephalitis virus infection
  • Western equine encephalitis

Clinical Information

  • ENCEPHALITIS VIRUS WESTERN EQUINE-. a species of alphavirus that is the etiologic agent of encephalomyelitis in humans and equines in the united states southern canada and parts of south america.
  • ENCEPHALOMYELITIS WESTERN EQUINE-. a form of arboviral encephalitis which primarily affects horses endemic to western and central regions of north america. the causative organism encephalomyelitis virus western equine may be transferred to humans via the bite of mosquitoes culex tarsalis and others. clinical manifestations include headache and influenza like symptoms followed by alterations in mentation seizures and coma. death occurs in a minority of cases. survivors may recover fully or be left with residual neurologic dysfunction including parkinsonism postencephalitic. from joynt clinical neurology 1996 ch26 pp8 9

Convert A83.1 to ICD-9

  • 062.1 - West equine encephalitis

Code Classification

  • Certain infectious and parasitic diseases (A00–B99)
    • Viral and prion infections of the central nervous system (A80-A89)
      • Mosquito-borne viral encephalitis (A83)

Code History

  • FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016
    (First year ICD-10-CM implemented into the HIPAA code set)
  • FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020

Information for Patients


Encephalitis is an inflammation of the brain. Usually the cause is a viral infection, but bacteria can also cause it. It can be mild or severe. Most cases are mild. You may have flu-like symptoms. With a mild case, you may just need rest, plenty of fluids, and a pain reliever.

Severe cases need immediate treatment. Symptoms of severe cases include

  • Severe headache
  • Sudden fever
  • Drowsiness
  • Vomiting
  • Confusion
  • Seizures

In babies, additional symptoms may include constant crying, poor feeding, body stiffness, and bulging in the soft spots of the skull.

Severe cases may require a stay in the hospital. Treatments include oral and intravenous (IV) medicines to reduce inflammation and treat infection. Patients with breathing difficulties may need artificial respiration. Some people may need physical, speech, and occupational therapy once the illness is under control.

NIH: National Institute of Neurological Disorders and Stroke

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Viral Infections

Viruses are very tiny germs. They are made of genetic material inside of a protein coating. Viruses cause familiar infectious diseases such as the common cold, flu and warts. They also cause severe illnesses such as HIV/AIDS, smallpox, and Ebola.

Viruses are like hijackers. They invade living, normal cells and use those cells to multiply and produce other viruses like themselves. This can kill, damage, or change the cells and make you sick. Different viruses attack certain cells in your body such as your liver, respiratory system, or blood.

When you get a virus, you may not always get sick from it. Your immune system may be able to fight it off.

For most viral infections, treatments can only help with symptoms while you wait for your immune system to fight off the virus. Antibiotics do not work for viral infections. There are antiviral medicines to treat some viral infections. Vaccines can help prevent you from getting many viral diseases.

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