# Presentation: 083321

## Laboratory Diagnosis of West Nile Virus Infections

## Distribution of Important Arboviruses in the U. S.

**Western Equine Encephalitis**

**Probably Highlands J**

**St. Louis Encephalitis**

**West Nile**

***Distribution of Important Arboviruses in the U. S.***

## Flaviviridae

**About 70 members, half of which are associated**
**with human disease**

**Enveloped, spherical virion, 40 - 50 nm **

**Two envelope proteins:   E and M (prM)**

**Icosahedral capsid, 25 - 30 nm**

**ssRNA genome, linear, positive polarity, 1.1 kb,**
**infectious**

## Members of the Japanese Encephalitis Virus Group

- Members of the
- Japanese Encephalitis Virus Group

**- Cacipacore virus**

**- Koutango virus**

**- Japanese encephalitis virus**

**- Murray Valley encephalitis virus**

**- Alfuy virus**

**- St. Louis encephalitis virus**

**- Usutu virus**

**- West Nile encephalitis virus**

**- Kunjin virus**

**- Yaounde virus**

## Human SLE Case Distribution by State1964 - 2001

**CT  1**

**DC  9**

**NJ  131**

**DE  1**

**MD 9**

**150**

**29**

**65**

**123**

**88**

**379**

**5**

**3**

**695**

**368**

**25**

**125**

**67**

**80**

**21**

**8**

**337**

**75**

**2**

**14**

**3**

**6**

**9**

**3**

**19**

**440**

**11**

**2**

**36**

**3**

**141**

**970**

**1**

**3**

**12**

**5**

**1**

**7**

**1990s**

**2000**

**2001**

## Diagnostic Assays for Arboviruses

**Mosquito pools, Tissues**

**Serological**
**Assays**

**Virus Detection**
**Assays**

**IgM ELISA**
**IgG ELISA**
**PRNT**
**CF**
**HI**
**IFA**
**Dipsticks**

**Virus isolation (cell culture, mice)**
**IFA**
**TaqMan RT-PCR**
**Ag-capture ELISA**
**RT-PCR / sequencing**
**Dipsticks**
**NASBA**

**WN virus is a**
**BSL-3 pathogen**

## Information needed for serological  testing and interpretation

- Information Needed for Serological

-  Testing and Interpretation

- Date of onset of disease

- Dates of sample collection

- Travel history

- Vaccination history

- Clinical encephalitis

## Long Term WN Virus IgM Activity in Human Serum

**Long-term WN Virus IgM Activity in Human Serum**

**NYCDOH-CDC Collaborative Study**

**N=29**

**7/12 (60%) of WN Encephalitis Virus Patients were IgM Positive at 500 Days Post-onset  **

**Long Term WN Virus IgM Activity in Human Serum**

**N = 29**

## WN Virus IgM Response in CSF

**0**

**5**

**10**

**15**

**20**

**25**

**30**

**35**

**40**

**45**

**50**

**55**

**60**

**65**

**70**

**75**

**80**

**85**

**90**

**Days Post-onset**

**0**

**5**

**10**

**15**

**20**

**25**

**30**

**35**

**40**

**P/N**

**N=31**

## Serological Analysis of A WN Case

**Patient**

**Days **

**P.I.**

**IgM **

**(WN)**

**IgG **

**(SLE)**

**WN**

**SLE **

**DEN2**

**JE**

**CSF**

**8**

**26.91**

**1.78**

**nd**

**nd**

**nd**

**nd**

**S1**

**9**

**9.1**

**4.16**

**160**

**20**

**<10**

**10**

**S2**

**34**

**6.7**

**4.62**

**1280**

**20**

**<10**

**20**

**Positive **

**Control**

**n.a.**

**9**

**6.5**

**>5120**

**2560**

**2560**

**320**

## WN Virus Antigen Detection Assays

**Virus Isolation**
**Antigen Detection**
**IFA – Mabs**
**Ag – Capture**
**Dipsticks**
**Immunohistochemistry**

## VecTestTM WNV/SLE Dipstick assay

**  **Procedure:

- VecTest strip

- 250 l mosquito
- pool suspension

- 15 min

## Molecular Amplification Assays

**Serum, CSF, Tissue, & Mosquito Pools**

**Standard**
**RT-PCR**

**TaqMan**
**RT-PCR**

**NASBA**

**SYBR Green**
**RT-PCR**

## Sensitivity of Virus Assays

**TaqMan/NASBA (0.1 PFU) > Isolation (1 PFU) >**
** ****Ag Capture (1000 PFU)**

## Appropriate Use of Nucleic Acid Detection Assays

- nucleic acid detection assays should
- _not_ be used as the sole diagnostic test, especially for serum samples.

## Meetings and Guidelines

**National Meetings on WN Virus**

- November 8 - 9, 1999, Ft. Collins, CO
- January 31 - February 4, 2001, Charlotte, NC
- March 22 - 23, 2002, Atlanta, GA

**WN Virus Guidelines**

- 2000, 2001, 2002

**Available at http://www.cdc.gov/ncidod/dvbid/westnile/publications.htm**