**Please forward this to all appropriate personnel within your institution**
This is a routine message from the Minnesota Department of Health (MDH) and the Minnesota Laboratory System (MLS). This message is being sent to MLS laboratory contacts serving Minnesota residents. You are not required to reply to this message.
Today MDH is announcing the first reported WNV case for 2005, marking the beginning of the West Nile virus season in Minnesota. The WadenaCounty resident had onset of illness on 6/22/2005, and presented with WN encephalitis. The press release is posted on the MDH Website at:
Note to laboratories that conduct WNV testing: MDH is not requesting that sera and/or CSF from positive tests be submitted to the MDH PHL, rather, all positive results must be reported to MDH Acute Disease Investigation and Control Section (ADIC) at 612-676-5414 or 1-877-676-5414
Physicians should also continue to call the ADIC at 612-676-5414 or 877-676-5414, to report ALL cases of WNV, as well as other arboviruses.
Priority for WNV Testing at MDH-PHL
MDH is concentrating its testing efforts and resources on patients who meet any of the following criteria:
- presumptive viral encephalitis/meningo-encephalits or aseptic meningitis
- fever and headache that warrants a lumbar puncture and/or hospitalization
- presumed Guillain-Barre syndrome or acute flaccid paralysis.
Please see the CDC website for additional WNV Clinical Guidance:
Process for WNV Testing by MDH-PHL
- MDH-PHL IS ONLY TESTING PATIENT SAMPLES THAT MEET THE ABOVE CRITERIA
- Routine WNV testing should be forwarded to your routine reference laboratories.
- WNV FDA approved serology tests are available at several reference laboratories
- Fee stickers are not required for WNV testing that meets the above criteria
Virology Specimen Submission Forms
When sending a specimen to MDH for WNV testing, please use the MDH Virology Specimen Submission Form by clicking this link or call MDH DASH at 612-676-5396. Form must be filled out completely, including but not limited to: the patient name, hospital name and phone number, specimen source, date of collection, and physician requesting the test. Also necessary, is documentation of patient symptom(s), duration of illness, and travel history. Please document this information under the “Test Requested” and “Clinical Symptoms” sections of the form.
Testing for WNV and other Arboviruses
When a specimen is submitted for WNV testing, the MDH-PHL conducts serology and real-time PCR for WNV, LaCrosse encephalitis (LAC), Eastern equine encephalitis (EEE), Western equine encephalitis (WEE), and St. Louis encephalitis (SLE). Vero cell culture is also performed which can detect these agents and other viral agents of encephalitis. All specimens should be shipped at refrigeration temperature.
Serum Testing
1. Test Requested (to be written on virology form): West Nile Virus Test - Serum
2. Specimen requirements: 1.0 - 2.0 ml of serum.
-Acute (< 10 days after onset) and Convalescent (2 - 4 weeks after onset) sera may be required because antibody to WNV (IgM and IgG) has been detected in patient samples for over a year following the onset of symptoms. Comparison of acute and convalescent antibody levels is required to demonstrate recent infection.
3. WNV Test - Serum: includes both [a] and [b] below
a. WNV EIA for IgG and IgM
Method: Standard CDCIgM antibody capture ELISA and IgG ELISA assays are used to detect antibody reactive against flaviviruses (WNV and SLE are flaviviruses and cannot be differentiated by this method).
Turn-around-time: 3 - 6 days.
b. Arbovirus IFA test
Method: Indirect Fluorescent Antibody Assay (IFA) for SLE, EEE, WEE, and LAC.
Turn-around-time: 2 days
Cerebral spinal fluid (CSF)Testing
1. Test Requested (to be written on virology form): West Nile Virus Test - CSF
2. Specimen requirements: 2.0 ml of CSF is required for all assays to be performed.
3. WNV Test - CSF includes [a, b and c] below: (in order of priority, based on specimen volume)
a. WNV EIA for IgM (considered the gold standard for diagnosis of WNV in CSF)
Method: Standard CDCIgM antibody capture ELISA assay is used to detect antibody reactive against flaviviruses.
Turn-around-time: 3 - 6 days.
b. Vero cell culture
Method: Standard virology culture methods on Vero cell lines
Turn-around-time: 10 days
c. Real-time PCR (note: RT-PCR has poor sensitivity for WNV in CSF)
Method: TaqMan PCR performed for WNV, LAC, EEE, WEE, and SLE
Turn-around-time: 2 - 3 days
Brain tissue and other material: Brain biopsy tissue (cortex, midbrain, brainstem, or other regions) and heart blood (autopsies) may be sent for testing. Turnaround times: 2 - 3 days (real-time PCR) and 10 days (cell culture).
WNV History in Minnesota – 2002-2004
Since WNV was first identified in 2002, 230 human cases were reported among residents of 59 MN counties. One hundred fifty-one (66%) case-patients were diagnosed with West Nile Fever (WNF), the less severe form of the disease; 41 (18%) had encephalitis; 37 (16%) had meningitis; and three (1%) had acute flaccid paralysis. Six WN encephalitis patients (age range, 51-86 years) died from their illness. Onset of illness ranged from June 18 to October 8, with an August peak in all three years. For further details on WNV in Minnesota, please see the following MDH link:
If you have any questions regarding WNV laboratory testing, please call Susan Fuller, Supervisor of the Virology Unit, at (612) 676-5255. Requests for testing or medical questions should be directed to our ADIC Section at (612) 676-5414 or 1-877-676-5414.
Paula M. Snippes, MT (ASCP)
Program Advisor, Minnesota Laboratory System,
MDH-Public Health Laboratory
Phone: 6126765258