Mosquito-borne disease surveillance report: July 28 to August 3, 2019 (Week 31)

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Date published: 2019-08-13

West Nile

Human Epidemiology

As of surveillance week 31, ending on August 3, 2019, one probable human case of West Nile virus (WNV) in Ontario has been reported to the Public Health Agency of Canada (PHAC) (Table 1).

Table 1. Year-to-Date (YTD) WNV human cases, by disease classification and province (January 1- August 3, 2019)
Province	Clinical Cases			Total ^{Footnote 1}	Asymptomatic Infections ^{Footnote 2}	YTD Grand Total	Rate(per 100,000) ^{Footnote 3}
Province	Neurological	Non-neurological	Unclassified	Total ^{Footnote 1}	Asymptomatic Infections ^{Footnote 2}	YTD Grand Total	Rate(per 100,000) ^{Footnote 3}
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	0	1	1	0	1	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 [0%]	0 [0%]	1 [100%]	1 [100%]	0	1	0
Footnote 1 Clinical cases are the sum of confirmed and probable: WNV neurological and non-neurological syndromes, along with any unclassified. Return to footnote 1 referrer 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. Return to footnote 2 referrer Footnote 3 Calculated with grand total of clinical and asymptomatic cases, using Statistics Canada 2018 population estimates. Return to footnote 3 referrer

Mosquito, Wild Bird & Equine Epidemiology

As of week 31, PHAC has been notified of 3, 775 mosquito pools tested for WNV. Of these, three were positive: two in Ontario and one in Manitoba (Table 2).

Seven of 26 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 not reported any domestic animals that tested positive for WNV (Table 3).

**Figure 1. (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**

Figure1 - footnotes

Footnote 1

Human cases includes clinical cases and asymptomatic infection.

Return to footnote 1 referrer

Footnote 2

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

Return to footnote 2 referrer

Footnote 3

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

Return to footnote 3 referrer

Table 2. Year-to-Date WNV positive pools and percent positive by province and nationally (January 1- August 3, 2019)
Province ^{Footnote 1}	Positive Pools	Total Pools Tested	Percent Positive
Saskatchewan	0	71	0.00 %
Manitoba	1	701	0.14 %
Ontario	2	2176	0.09 %
Québec	0	827	0.00 %
Total	3	3775	0.08 %
Footnote 1 Mosquito surveillance data is reported by the following four provinces: Saskatchewan, Manitoba Ontario and Quebec. Return to footnote 1 referrer

Table 3. Number of WNV positive animal cases for current week and year to date (January 1- August 3, 2019)
Province	Wild Birds ^{Footnote 1}		Equine
Province	Week 31	Year-to-Date Total	Week 31	Year-to-Date Total
British Columbia	0	0	0	0
Alberta	0	0	0	0
Saskatchewan	0	0	0	0
Manitoba	0	0	0	0
Ontario	0	4	0	0
Québec	1	3	0	0
Maritime Provinces	0	0	0	0
Territories	0	0	0	0
Total	1	7	0	0
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. Return to footnote 1 referrer

California Serogroup

As of August 3, 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 not reported any horses testing positive for Eastern Equine Encephalitis virus (EEEV) in Canada.

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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Date modified:: 2021-07-02

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