Mosquito-borne disease surveillance report: September 27 to October 24, 2020 (Week 40 to 43)

West Nile

Human epidemiology

As of surveillance week 43, ending on October 24, 2020, eighty-six human cases of West Nile virus (WNV) have been reported to the Public Health Agency of Canada (PHAC) (Table 1). Of these, three are reported as deaths.

Table 1. West Nile virus human cases, by disease classification and province (January 1 - October 24, 2020)

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
Ontario	9	27	26	62	1	63	0.43
Quebec	6	0	13	19	4	23	0.27
Total	15	27	39	81	5	86	0.23
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 2020 Q1 population estimates. Return to footnote 3 referrer

Mosquito, wild bird and equine epidemiology

As of week 43, PHAC has been notified of 15,945 mosquito pools tested for WNV in Canada. Of these, there have been five WNV-positive mosquito pools identified in Manitoba, 171 in Ontario, and twenty-two in Québec (Table 2).

Forty dead wild birds have tested positive for WNV, by the Canadian Wildlife Health Cooperative one in Saskatchewan, twenty-one in Ontario and seventeen in Québec (Table 3).

Since the start of this season, the Canadian Food Inspection Agency (CFIA) has identified six equine cases that tested positive for WNV, one in Alberta, two in Saskatchewan, one in Ontario, one in Quebec and one in Manitoba (Table 3).

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Figure 2 - Text equivalent

Between January 1 and October 24, 2020, eighty-six human cases associated with West Nile virus acquired in Canada were reported to PHAC. Thirty-eight birds and 1.24% of mosquito pools have tested positive for WNV in Canada and reported to PHAC.

Table 2. Year-to-Date WNV positive pools and percent positive by province and nationally (January 1 - October 24, 2020)

ProvinceFootnote 1	Positive pools	Total pools tested	Percent positive
Saskatchewan	0	71	0.00 %
Manitoba	5Footnote *	1,264	0.40 %
Ontario	171	13,179	1.30 %
Québec	22	1,264	1.54 %
Total	198	15,945	1.24 %
Footnote 1 Mosquito surveillance data is reported by the following 4 provinces: Saskatchewan, Manitoba Ontario and Quebec. Return to footnote 1 referrer Footnote 2 No WNV infected mosquito pools have been found as part of Manitoba Health’s West Nile virus surveillance program, which submits information to PHAC, however two (2) positive mosquito pools were detected by another surveillance program in the Prairie Mountain Health Region. Return to footnote * referrer

Table 3. Number of WNV positive equine and birds by province and nationally (January 1 - October 24, 2020)

Province	Wild birds Footnote 1	Equine
British Columbia	0	0
Alberta	0	1
Saskatchewan	1	2
Manitoba	0	1
Ontario	22	1
Quebec	17	1
Maritime provinces	0	0
Territories	0	0
Total	40	6
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 October 24, 2020, 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 2020 transmission season.

The CFIA has reported eight horses testing positive for Eastern Equine Encephalitis virus (EEEV) in Ontario.

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.