Surveillance & Environmental Health

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

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 Dead-end Hosts: Humans & other vertebrates Reservoir, Introductory & Amplifying Hosts: Birds 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. West Nile virus history 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

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

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.

15. Blood Work

16. Seroprevalence:

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