Eastern equine encephalitis virus is the most deadly encephalitic arbovirus in North America, with a case fatality rate of 30% to 50%.
Occurs mainly in North America, around the eastern seaboard and Gulf coast states, and is transmitted by mosquitoes.
Diagnosis is based on clinical presentation and geographical clues. Confirmation of diagnosis is via serological testing. It is a notifiable condition.
There is no specific treatment; supportive care with management of specific symptoms is recommended.
Eastern equine encephalitis virus (EEEV) is a positive-sense single-stranded RNA virus (family: Togaviridae; genus: Alphavirus) transmitted by mosquitoes.
In humans infected with EEEV, the incubation period ranges from 4 to 10 days, and duration of acute illness is typically days to weeks depending on severity.
Humans infected with EEEV may be asymptomatic, or they may develop symptoms that resemble influenza or dengue fever (e.g., fever, malaise, headache, nausea) with or without neuroinvasive symptoms (e.g., altered mental status, seizures). The mortality rate for humans with neuroinvasive disease is approximately 30% to 50%.
History and exam
Key diagnostic factors
- presence of risk factors
- fever (≥37.5°C)
Other diagnostic factors
- neck stiffness (nuchal rigidity)
- focal weakness (decreased motor function)
- abdominal pain
- altered mental status
- cranial nerve palsy
- cerebral oedema
- intracranial hypertension
- aseptic meningitis
- haemophagocytic lymphohistiocytosis
- 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)
1st investigations to order
- enzyme-linked immunosorbent assay (ELISA)
- MRI brain
- plaque reduction neutralisation test (PRNT)
- basic metabolic panel
Investigations to consider
- cerebrospinal fluid (CSF) studies
- CT brain
- West Nile virus infection
- La Crosse virus infection
- St Louis encephalitis
- 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
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