For Health Professionals
- West Nile Virus in Vermont
Who Should Be Tested for West Nile Virus?
Hospitalized patients with encephalitis, meningitis of suspected viral origin, or Guillain-Barré syndrome should be tested. Testing is not recommended for persons with mild illness, such as fever or headache, because levels of West Nile virus activity in the community would have to be very high for such symptoms to likely be due to West Nile virus infection.
Knowledge of the etiology is not required for establishing a care plan for mild illness. These persons should be advised to seek medical attention if more severe symptoms develop such as confusion, severe muscle weakness, lethargy, severe headache, stiff neck, or photophobia.
Specimen Collection and Transport for Hospitalized Patients
Acute and convalescent serum
Collect 7-10 ml of blood in a red-top or tiger-top collection tube. Acute phase serum should be collected on day 10 of illness, as most cases have detectable serum IgM antibody by the eighth day of illness. Convalescent serum should be collected on day 21 of illness; most infected individuals demonstrate long-lived serum IgG antibody by three weeks post infection. Any patient whose acute phase serum tests negative for IgM antibody needs to have a convalescent phase specimen submitted for testing. Specimens should be centrifuged and 1-2 ml of serum submitted at refrigerated temperature to the Vermont Department of Health Laboratory.
Cerebrospinal fluid
Collect 1-2 ml of cerebrospinal fluid (CSF) as early as possible. IgM antibody is detectable in CSF in most (99%) patients by the onset of symptoms, but is relatively short-lived in CSF compared with serum. Detection of IgM in CSF confirms recent infection with West Nile virus, although infection cannot be definitively ruled out if IgM is not detected. IgG antibody in CSF often does not reach detectable levels and is therefore not a sensitive indicator of infection. Specimens should be submitted frozen to the Vermont Department of Health Laboratory.
All specimens should be accompanied by a completed form VDHL" Micro 222 Clinical Test Form” and a CDC History Form. Mark "WNV antibody" under the heading "Serology Tests (Misc.)". Date of onset must be included.
Forms and serology mailers can be obtained by contacting the VDHL at (800) 660-9997, extension 7560.