1. Surveillance & Environmental Health West Nile Virus Seroprevalence: Results of Enhanced Surveillance Program

2. Goals of the sero-survey Compliment to regular clinical data Provides baseline infection rate and change over time Identifies risk factors of WNv infection Lessons learned can be transferred to new arthropod borne viruses

3. Vectors: Mosquitoes Reservoir, Introductory & Amplifying Hosts: Birds Dead-end Hosts: Humans & other vertebrates West Nile virus Transmission Cycle

4. Illness in Humans ► Majority experience very mild or no symptoms ► WNv Non-neurological Syndrome: Flu like symptoms: fever, headache, body aches, rash ► WNv Neurological Syndrome: Encephalitis, meningitis, acute flaccid paralysis, often with long term effects

5. 1937: Virus first identified in the West Nile province of Uganda. 1990s: more virulent strain emerged in North Africa; outbreaks in Europe and the Middle East (e.g., Romania, Russia, Israel) 1999: WNv found in New York, USA 2000: Surveillance for WNv begins in Canada (birds, mosquitoes, humans, horses) 2001: first detected in Ontario, Canada in birds and mosquitoes 2002: human cases detected in Ontario and Quebec 2003: first human cases in MB, SK, and AB West Nile virus history

6. Distribution in the US: 2006

7. National distribution 2002 Source: West Nile Virus Monitor - PHAC

8. National distribution 2003 Source: West Nile Virus Monitor - PHAC

9. National distribution 2004 Source: West Nile Virus Monitor - PHAC

10. National distribution 2005 Source: West Nile Virus Monitor - PHAC

11. National distribution 2006 Source: West Nile Virus Monitor - PHAC

12. National distribution 2007 Source: West Nile Virus Monitor - PHAC

13. Foothills Grassland Parkland Rocky Mountain Natural Regions Health Region Boundaries Boreal Forest Canadian Shield West Nile virus Geographic Distribution of Clinical Cases Human Cases 1 - 2 3 - 6 7 - 12 13 - 24 25 - 61

14. PURPOSE To estimate how many Albertans have been exposed to WNv To assess knowledge, attitudes and personal protective behaviours METHODS Short telephone KAB survey Blood requisition sent to participants Blood screened in AB Provincial Lab of Microbiology, then positives confirmed at the National Lab of Microbiology in Winnipeg, MB. PARTICIPATION RATE 2004 Laboratory requisitions mailed3,780 Blood samples received at Provincial Lab 2,518 Response rate67% PARTICIPATION RATE 2007 Laboratory requisitions mailed3,243 Blood samples received at Provincial Lab 1,955 Response rate60%

15. Blood Work Test NameFormatInterpretation WNv IgM (Immunoglobulin M) Enzyme Immunoassay (EIA) for WNv IgM in serum Relatively specific for WNv Persists >9months in at least 2/3 of cases WNv IgG (Immunoglobulin G) EIA for WNv IgG in serum Cannot differentiate WNv from other flaviviruses Rising IgG levels suggest recent flavivirus infection/vaccination PRNT: Plaque Reduction Neutralization Titres Measures ability of serum to block live WNv High specificity for WNv ‘Gold Standard ‘ Takes 4-8 weeks to perform test.

16. Seroprevalence: Year: 2004 Seroprevalence Point estimate (95% CI) Urban Rest of Alberta 0 Palliser Region 0.77% (0.28, 1.41) Rural Rest of Alberta 0.84% (0.20, 1.82) Palliser Region 4.56% (2.79, 6.77) Alberta (total) 0.31% (0.12, 0.58) Year: 2007 Urban Rest of Alberta 1.00% (0.00, 2.50) Palliser Region 1.76% (0.73, 2.79) Rural Rest of Alberta 0.74% (0.00, 1.61) Palliser Region 4.16% (2.31, 6.01) Alberta (total) 1.52% (0.86, 2.18)

17. Seroprevalence: 2004 ~ 6900 Albertans infected with WNv ~1/26 infected became clinical cases in 2003 ~1/142 infected developed severe illness in 2003 2007 ~34,247 Albertans infected with WNv ~1/856 infected became clinical cases in 2006 ~1/1631 infected developed severe illness in 2006 Note: these numbers relate to the year previous the study because we tested for seropositivity that occurred prior to the study year

18. Conclusions Seroprevalence appears to have increased between the two study periods Estimates of the absolute numbers of seropositive Albertans has increased due to the occurrence of urban positive samples The proportion of seropositive cases that became clinical appears to have reduced since the virus first appeared in the province The proportion of seropositive cases that become clinical is very low Future sero-surveys will be needed to corroborate these findings

19. Contact Information Surveillance and Environmental Health Public Health Division Alberta Health and Wellness P O Box 1360 Station Main Edmonton, AB T5J 2N3 CANADA Telephone:1.780.427.4518 Facsimile:1.780.427.1470 E-mail:Health.Surveillance@gov.ab.ca Internet:www.health.gov.ab.ca