Eastern equine encephalitis virus infection

Last reviewed: 22 Feb 2023
Last updated: 13 Nov 2020



History and exam

Key diagnostic factors

  • presence of risk factors
  • fever (≥37.5°C)
  • headache
  • seizures
More key diagnostic factors

Other diagnostic factors

  • nausea/vomiting
  • myalgias/arthralgias
  • neck stiffness (nuchal rigidity)
  • focal weakness (decreased motor function)
  • photophobia
  • abdominal pain
  • altered mental status
  • cranial nerve palsy
  • tremors
  • drowsiness
  • meningismus
  • diarrhoea
  • cerebral oedema
  • intracranial hypertension
  • aseptic meningitis
  • haemophagocytic lymphohistiocytosis
  • hemiparesis
Other diagnostic factors

Risk factors

  • travel/residence in endemic areas
  • working in endemic areas
  • outdoor recreational activities in endemic areas
  • seasonal factors favouring breeding of mosquitoes
  • age <15 years or >50 years
  • occupational exposure (laboratory)
  • bioterrorism
More risk factors

Diagnostic investigations

1st investigations to order

  • enzyme-linked immunosorbent assay (ELISA)
  • MRI brain
  • plaque reduction neutralisation test (PRNT)
  • FBC
  • basic metabolic panel
More 1st investigations to order

Investigations to consider

  • cerebrospinal fluid (CSF) studies
  • CT brain
  • electroencephalogram
More investigations to consider

Treatment algorithm


symptomatic patients



Amy Vittor, MD, PhD

Assistant Professor

Division of Infectious Disease and Global Medicine

University of Florida




AV is funded by the National Institute of Allergy and Infectious Diseases (NIAID) for work on host susceptibility and emerging alphaviruses (2016-2021); however, the funding supports new insights in the field only, it does not directly impact any articles produced. AV is a recipient of an NIH NIAID K08 award. AV is also the author of a reference cited in this topic.

Peer reviewers

Miguel G. Madariaga, MD, MSc, FACP

Infectious Diseases Consultant

Naples Community Hospital




MGM declares that he has no competing interests.

Stalin Vilcarromero, MD

Research Physician

US Naval Medical Research Unit 6 (NAMRU-6)




SV declares that he has no competing interests.

  • Eastern equine encephalitis virus infection images
  • Differentials

    • West Nile virus infection
    • La Crosse virus infection
    • St Louis encephalitis
    More Differentials
  • Guidelines

    • Consensus guidelines for the investigation and management of encephalitis in adults and children in Australia and New Zealand
    • Management of suspected viral encephalitis in children
    More Guidelines
  • padlock-lockedLog in or subscribe to access all of BMJ Best Practice

Use of this content is subject to our disclaimer