Last reviewed: 24 Jan 2021
Last updated: 13 Nov 2020



History and exam

Key diagnostic factors

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

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

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

Diagnostic investigations

1st investigations to order

  • enzyme-linked immunosorbent assay (ELISA)
  • MRI brain
  • plaque reduction neutralisation test (PRNT)
  • FBC
  • basic metabolic panel

Investigations to consider

  • cerebrospinal fluid (CSF) studies
  • CT brain
  • electroencephalogram

Treatment algorithm


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 reviewersVIEW ALL

Infectious Diseases Consultant

Naples Community Hospital




MGM declares that he has no competing interests.

Research Physician

US Naval Medical Research Unit 6 (NAMRU-6)




SV declares that he has no competing interests.

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