For Health Professionals — Arboviral Diseases

Disease-specific Clinical Information
Cause, Prevalence, Transmission, Symptoms, Testing and Diagnosis

All EEE and WNV disease cases should be reported to the Vermont Department of Health.

Criteria for Arboviral Testing

In the summer and fall, patients with asceptic encephalitis or meningitis should be tested for both West Nile virus and Eastern equine encephalitis virus. Patients with Guillain-Barré syndrome should also be tested for West Nile virus. Testing is not recommended for persons with mild illness, such as fever or headache, because levels of WNV and EEEV activity in the community would have to be very high for such symptoms to likely be due these viral infections.

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Diagnostic Testing

Serologic testing remains the primary method for diagnosing WNV and EEEV infection. Combined with a consistent clinical presentation in an endemic area, a rapid and accurate diagnosis of acute arboviral disease can be made by the detection of virus-specific IgM antibody in serum or CSF. However, samples taken early in the course of illness may be negative, and a convalescent sample may be necessary for accurate diagnosis.

Ideal timing of specimens for serology:




3 to 10 days after onset of symptoms


2-3 weeks after acute sample

At least 1.0 of serum and/or 1.0 mL of CSF is required for serology testing

WNV and EEE virus antibody tests are available commercially. However, a positive IgM test result should be confirmed by neutralizing antibody testing at a state public health laboratory or CDC.

Samples can be sent to the Vermont Department of Health Laboratory. Serum should be refrigerated and shipped with an ice pack, and CSF samples should be submitted frozen. All specimens should be accompanied by a completed VDHL "Clinical Test Request Form.

Mark "WNV and or EEE virus antibody" under the heading "Serology Tests (Misc.)." Date of onset must be included.

Forms and serology mailers can be obtained by contacting the Vermont Department of Health Laboratory at 800-660-9997, extension 7560.

All EEE and WNV disease cases should be reported to the Vermont Department of Health.

Contact Us

Department of Health
Tel: 800-640-4374 (Vermont only) or 802-863-7240
Email the Department of Health (general mailbox)

Public Health Laboratory
Tel: 800-660-9997, extension 7560

Epidemiology Field Unit
800-640-4374 (in VT only), or 802-863-7240.

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