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Public Health Laboratory

    

Contact Information
Los Angeles County
Department of Public Health
Public Health Laboratory
12750 Erickson Avenue
Downey, California 90242

Laboratory Director
Nicole M. Green, Ph.D, D(ABMM)

Phone: (562) 658-1300
Fax: (562) 401-5999

Monday - Friday
8:00 AM to 5:00 PM
Saturday
8:00 AM to 4:30 PM

West Nile Virus Testing

Culex sp.

West Nile virus (WNV) infection is caused by a virus transmitted by mosquitos. Culex sp. mosquitos are known to transmit West Nile virus which is the most common arthropod-borne virus (arbovirus) identified in California.

Many factors influence when and where West Nile virus outbreaks occur including weather, number of birds that maintain the virus, number of infected mosquitoes, and human behavior. Updates on the latest West Nile virus activity can be found at http://www.westnile.ca.gov/. Additional information on West Nile virus including prevention tips, mosquito control, healthcare provider guidance, and surveillance maps, is located at http://www.cdc.gov/westnile/index.html. For dead bird reporting, please contact the California State West Nile Virus program at 877-WNV-BIRD (877-968-2473).   

The Los Angeles County Public Health Laboratory (PHL) performs EIA testing for WNV on hospitalized patients or those evaluated in an emergency department setting with aseptic meningitis, encephalitis, acute flaccid paralysis syndrome (atypical Guillain-Barré syndrome) and outpatients with possible WNV fever. Public Health laboratory services are also available for confirmatory testing of West Nile virus positive results on serum specimens.

For WNV serology, parallel testing of acute and convalescent serum specimens is preferred. Specimens should be marked clearly as "acute" and "convalescent."  The optimal time for collection of acute blood is as soon as arboviral disease is suspected and up to 7 days after symptom onset. If the IgM is negative in the serum sample and WNV is highly suspected, another serum sample should be collected 2-3 days after the first serum. Convalescent serum specimens should be collected 10-30 days after symptom onset. WNV IgM is usually present in immunocompetent individuals by day 5 of illness onset. For immunocompromised patients, WNV antibody response may be delayed.

Additional serological and molecular testing for WNV on serum and CSF is available through the California Department of Public Health - Viral and Rickettsial Diseases Laboratory (VRDL).  VRDL also performs CSF testing for other etiologies causing aseptic meningitis or encephalitis.

Specimens wished to be sent to VRDL should also include a State laboratory test request form in addition to a completed Los Angeles County Public Health Laboratory test request form. Current forms can be downloaded from the following websites:

http://www.cdph.ca.gov/programs/vrdl/Pages/CurrentVRDLSpecimenSubmittalforms.aspx

http://publichealth.lacounty.gov/lab/labforms.htm.

Completed test request form(s) should accompany each specimen type. Each specimen must be labeled with the patient name and a second identifier (date of birth or medical record number), date of collection, and specimen type.  Include a copy of previous test results and any pertinent patient history with the specimen including onset date. Send specimens by courier or overnight shipper using the appropriate transport conditions for the specimen type. Ship packages Monday-Thursday to avoid weekend deliveries. Frozen specimens should be shipped on dry ice.

Acceptable specimen types and required specimen volumes are shown below. Samples should be transported on cold packs as soon as possible following collection. If samples cannot be transported immediately, they may be held at 4-8°C for up to 72 hours before shipping. Otherwise, specimens should be frozen at -70°C and shipped on dry ice.

Test Name

Performing Lab

Specimen Type

Specimen Requirement

WNV EIA, IgM and IgG

PHL

Serum

5-7 mL collected in red top or serum separator tube

WNV EIA, IgM and IgG

VRDL

Serum

5-7 mL collected in red top or serum separator tube

WNV EIA, IgM only

VRDL

CSF

2-3 mL

WNV IFA, IgM and IgG

VRDL

Serum

5-7 mL collected in red top or serum separator tube

Plaque reduction neutralization

VRDL

Serum

5-7 mL collected in red top or serum separator tube

WNV real-time PCR

VRDL

CSF

2-3 mL

WNV real-time PCR
(non-diagnostic purposes only)

VRDL

Serum, acute

5-7 mL collected in red top or serum separator tube

Enterovirus real-time PCR

VRDL

CSF

2-3 mL

Herpes real-time PCR

VRDL

CSF

2-3 mL

Also refer to Acute Communicable Disease Control's letter to physicians and laboratories (WestNileVirus.pdf).
 
 
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