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Mosquito-borne disease surveillance report: August 4 to 10, 2019 (Week 32)

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Organization: Health Canada

Date published: 2019-08-20

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Year-to-Date Snapshot
Year-to-Date Snapshot - Text Equivalent

Between January 1, 2019 and August 10, 2019, two human cases associated with West Nile virus in Canada have been reported to the Public Health Agency of Canada. Seven WNV-positive birds, eight WNV-positive mosquito pools, and one WNV-positive horse have been reported to date.

West Nile

Human Epidemiology

As of surveillance week 32, ending on August 10, 2019, two human cases of West Nile virus (WNV) have been reported to the Public Health Agency of Canada (PHAC) in Ontario (Table 1).

Table 1. Year-to-Date (YTD) WNV human cases, by disease classification and province (January 1- August 10, 2019)
Province Clinical Cases Total Footnote 1 Asymptomatic Infections Footnote 2 YTD Grand Total Rate(per 100,000) Footnote 3
Neurological Non-neurological Unclassified
British Columbia 0 0 0 0 0 0 0
Alberta 0 0 0 0 0 0 0
Saskatchewan 0 - - 0 0 0 0
Manitoba 0 0 0 0 0 0 0
Ontario 0 1 0 1 1 2 0
Québec 0 0 0 0 0 0 0
Maritime Provinces 0 0 0 0 0 0 0
Territories 0 0 0 0 0 0 0
Total 0 1 0 1 1 2 0
Footnote 1

Clinical cases are the sum of confirmed and probable: WNV neurological and non-neurological syndromes, along with any unclassified.

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Footnote 2

Satisfies WNV diagnostic test criteria in the absence of clinical criteria (i.e., asymptomatic blood donors whose blood is screened by blood operators, Canadian Blood Services or Héma-Québec.

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Footnote 3

Calculated with grand total of clinical and asymptomatic cases, using Statistics Canada 2018 population estimates.

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Figure 1. Geographic distribution of WNV human clinical cases and asymptomatic infections in Canada, 2019
Figure 1 - Text Equivalent

Between January 1, 2019 and August 10, 2019, two human cases associated with West Nile virus in Canada were reported to PHAC.

Mosquito, Wild Bird & Equine Epidemiology

As of week 32, PHAC has been notified of 5,149 mosquito pools tested for WNV. Of these, eight (0.16%) were positive: one in Quebec, five in Ontario and two in Manitoba (Table 2).

Seven of 27 dead wild birds have tested positive for WNV, by the Canadian Wildlife Health Cooperative (CWHC): four in Ontario and three in Quebec (Table 3).

Since the start of this season, the Canadian Food Inspection Agency (CFIA) has reported one horse that tested positive for WNV in British Columbia (Table 3).

Figure 2. (A) WNV human clinical cases and asymptomatic infections, (B) positive WNV birds, and (C) percent positive mosquito pools by episode or report week, in Canada, 2019
Figure 2 - Text Equivalent

Between January 1, 2019 and August 10, 2019, two human cases associated with West Nile virus in Canada were reported to PHAC. A total of seven birds and 0.16% of mosquito pools have tested positive for WNV in Canada and reported to PHAC.

Figure 2 - footnotes

Footnote 1

Human cases includes clinical cases and asymptomatic infection.

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Footnote 2

Episode week is based on symptom onset or best available date including: diagnosis, lab sample or date reported.

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Footnote 3

Episode week is based off date of death or best available date including: date found, submitted, or received.

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Table 2. Year-to-Date WNV positive pools and percent positive by province and nationally (January 1- August 10, 2019)
Province Footnote 1 Positive Pools Total Pools Tested Percent Positive
Saskatchewan 0 116 0.00 %
Manitoba 2 899 0.22 %
Ontario 5 3189 0.16 %
Québec 1 945 0.11 %
Total 8 5149 0.16 %
Footnote 1

Mosquito surveillance data is reported by the following four provinces: Saskatchewan, Manitoba Ontario and Quebec.

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Table 3. Number of WNV positive animal cases for current week and year to date (January 1- August 10, 2019)
Province Wild Birds Footnote 1 Equine
Week 32 Year-to-Date Total Week 32 Year-to-Date Total
British Columbia 0 0 1 1
Alberta 0 0 0 0
Saskatchewan 0 0 0 0
Manitoba 0 0 0 0
Ontario 0 4 0 0
Québec 0 3 0 0
Maritime Provinces 0 0 0 0
Territories 0 0 0 0
Total 0 7 1 1
Footnote 1

Not all provinces conduct dead wild bird surveillance as part of their respective WNV surveillance program. However, WNV positive dead wild birds may be identified through the National Wildlife Disease Surveillance Program, CWHC or by specific provinces.

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California Serogroup

As of August 10, 2019, no human exposures or cases of California serogroup virus have been reported by the National Microbiology Laboratory.

Eastern Equine Encephalitis

No human cases of EEEV have been reported to PHAC since the beginning of the 2019 transmission season.

The CFIA has reported one horse tested positive for Eastern Equine Encephalitis virus (EEEV) in Ontario.

Provincial/Territorial & International Surveillance Links

Data reported to PHAC is subject to change and may differ from provincial webpages due to reporting timelines. To obtain the latest arbovirus surveillance data, please refer to the following jurisdictional/regional webpages:

Provincial

International

Notes

Thank you to all our partners for participating in the National WNV/MBD surveillance program.

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