Mosquito-borne disease surveillance report: September 15 to 28, 2019 (Week 38 & 39)

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Organization: Public Health Agency of Canada

Date published: 2019-10-11

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Year-to-date snapshot
Year-to-date snapshot - Text equivalent

Between January 1, 2019 and September 28, 2019, 13 human cases of West Nile virus (WNV) have been reported to the Public Health Agency of Canada (PHAC). Twenty-seven WNV-positive birds, 88 WNV-positive mosquito pools, and 5 WNV-positive horse have been reported. In addition, six horses have tested positive for eastern equine encephalitis virus (EEEV) to date.

West Nile

Human epidemiology

As of surveillance week 39, ending September 28, 2019, 13 human cases of West Nile virus (WNV) have been reported to the Public Health Agency of Canada (PHAC) (Table 1). Of these, four cases reported travel outside of Canada: British Columbia (1), Alberta (2) and Ontario (1).

Table 1. Year-to-date (YTD) WNV human cases, by disease classification and province (January 1 - September 28, 2019)
Province Clinical cases Total of clinical cases Footnote 1 Asymptomatic infections Footnote 2 YTD grand total Rate (per 100,000) Footnote 3
Neurological Non-neurological Unclassified
British Columbia 0 1 0 1 0 1 0.02
Alberta 2 2 0 4 0 4 0.09
Saskatchewan 0 - - 0 0 0 0.00
Manitoba 0 0 0 0 0 0 0.00
Ontario 1 3 2 6 1 7 0.05
Quebec 1 0 0 1 0 1 0.01
Maritime provinces 0 0 0 0 0 0 0.00
Territories 0 0 0 0 0 0 0.00
Total 4 6 2 12 1 13 0.04
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

Since the start of the transmission season, ten human cases of WNV have been reported to PHAC.

Mosquito, wild bird and equine epidemiology

As of week 39, PHAC has been notified of 11,091 mosquito pools tested for WNV. Of these, 88 (0.79%) were positive in Quebec (12), Ontario (70) and Manitoba (6) (Table 2).

Twenty-seven of 58 dead wild birds have tested positive for WNV, by the Canadian Wildlife Health Cooperative (CWHC) in Saskatchewan (1), Ontario (18) and Quebec (8) (Table 3).

Since the start of this season, the Canadian Food Inspection Agency (CFIA) has reported 5 horses that tested positive for WNV in British Columbia (1), Saskatchewan (1), Alberta (1), Ontario (1) and Quebec (1) (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

Since the start of the transmission season, 10 human cases of West Nile virus have been reported to PHAC. A total of 27 birds and 0.79% 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 - September 28, 2019)
Province Footnote 1 Positive pools Total pools tested Percent positive
Saskatchewan 0 200 0.00 %
Manitoba 6 1,166 0.51 %
Ontario 70 8,226 0.85 %
Québec 12 1,499 0.80 %
Total 88 11,091 0.79 %
Footnote 1

Mosquito surveillance data is reported by the following 4 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 - September 28, 2019)
Province Wild birds Footnote 1 Equine
Week 38 & 39 Year-to-date total Week 38 & 39 Year-to-date total
British Columbia 0 0 0 1
Alberta 0 0 0 1
Saskatchewan 0 1 0 1
Manitoba 0 0 0 0
Ontario 0 18 0 1
Quebec 2 8 0 1
Maritime provinces 0 0 0 0
Territories 0 0 0 0
Total 2 27 0 5
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 September 28, 2019, no human exposures or cases of California serogroup virus have been reported by the National Microbiology Laboratory.

Eastern equine encephalitis

The CFIA has reported 6 horses that tested positive for eastern equine encephalitis virus (EEEV) in Ontario.

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

Provincial/territorial and 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:

Notes

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

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