West Nile Virus national surveillance report: September 16 to 22, 2018

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Organization: Public Health Agency of Canada

Published: October 15, 2018

ISBN: 2368-2841

West Nile Virus - Week 38 2018

Canada

Human

During surveillance week 38, ending on September 22, 2018, 56 clinical cases of West Nile virus (WNV) were retrospectively reported to the Public health Agency of Canada (PHAC). A number of other possible infections remain under investigation.

As of week 38, a total of 216 clinical cases of WNV have been reported by the following four provinces: Alberta (37), Manitoba (29), Ontario (88), and Québec (62). Of these, 98 (45%) have been classified as WNV neurological syndrome, 71 (33%) as WNV non-neurological syndrome and 47 (22%) as unspecified. Nine deaths have been reported. In addition, 18 WNV asymptomatic infections have been reported: Alberta (5), Manitoba (3), Ontario (5), and Québec (5).

Mosquito

To date (week 38), the PHAC has been notified of 16,814 mosquito pools tested for WNV: Saskatchewan (761), Manitoba (1,924), Ontario (12,581), and Québec (1,548). Of these, 561 (3.34%) pools have tested positive for WNV: 50 in Saskatchewan, 168 in Manitoba, 304 in Ontario, and 39 in Québec.

Wild Bird

To date, eighty-seven out of 177 dead wild birds have tested positive for WNV by the Canadian Wildlife Health Cooperative (CWHC), Manitoba Agriculture and British Columbia Ministry of Agriculture-Animal Health Centre: British Columbia (2), Saskatchewan (3), Manitoba (14), Ontario (28), and Québec (40). In addition, 12 live wild birds in Québec have tested positive for WNV by the University of Montréal.

Equine

The Canadian Food Inspection Agency (CFIA) has reported 109 horses with West Nile fever in the following five provinces: British Columbia (1), Alberta (68), Saskatchewan (30), Manitoba (6), and Ontario (4).

United States and U.S. territories

As of September 18^th, 1,077 human cases of WNV have been reported to the US Centers for Disease Control and Prevention (CDC). Of these 608 (56%) were classified as neuroinvasive disease and 469 (44%) as non-neuroinvasive disease. Thirty-five deaths have been reported. In addition, 196 presumptive viremic blood donors have been identified.

Europe and Neighboring Countries

As of September 27^th, 1,670 human cases of West Nile fever have been reported to the European Centre for Disease Prevention and Control. One hundred and twenty-four deaths have been reported.

Weekly updates: 2018 West Nile fever transmission season.

Other Mosquito-borne Diseases in Canada - Week 38 2018

Eastern Equine Encephalitis virus: The CFIA has reported 11 horses testing positive for Eastern Equine Encephalitis virus (EEEV) in Ontario. No human cases of EEEV have been reported to the PHAC during the 2018 season.
California Serogroup virus: Since May 1, 2018, 23 human cases/exposures of California serogroup virus have been reported by the National Microbiology Laboratory in the following seven provinces: Alberta (1), Saskatchewan (4), Manitoba (1), Ontario (5), Quebec (5), New Brunswick (5), and Nova Scotia (2). Additional work to further type these as Jamestown Canyon virus or Snowshoe hare virus is on-going.

Figure and tables

Figure 1. Text version below. — **Figure 1: Geographic distribution of WNV human clinical cases and asymptomatic infections in Canada, 2018**

Figure 2. Text version below. — **Figure 2: WNV human clinical cases and asymptomatic infections in Canada by report week^{Footnote ±}, 2018**

Table showing human clinical cases and asymptomatic infections associated with WNV in Canada, by province or territory and by week monitoring, dated September 15, 2018
Province / Territory	Report Week^{figure 2 table note ±}	Total
Alberta	0	0	0	0	0	0	0	0	0	0	0	1	6	12	14	7	2	0	0	-	-	-	-	-	-	-	-	-	42
Manitoba	0	0	0	0	0	0	0	0	0	1	2	1	5	10	6	3	4	0	0	-	-	-	-	-	-	-	-	-	32
Ontario	0	1	0	0	0	0	0	0	1	4	4	6	9	17	17	13	13	8	0	-	-	-	-	-	-	-	-	-	93
Quebec	0	0	0	0	0	0	0	0	0	1	1	7	10	15	7	12	7	1	0	-	-	-	-	-	-	-	-	-	67
Total	0	1	0	0	0	0	0	0	1	6	7	15	30	54	50	35	26	9	0	0	0	0	0	0	0	0	0	0	234
'-' = Not available. Figure 2 table notes Figure 2 table note ± WNV clinical cases and asymptomatic infections are grouped by report week, based on episode date. Episode date could include one of the following: onset date, diagnosis date, lab sample date or reporting date. Return to figure 2 table note ± referrer

Figure 3. Text version below. — **Figure 3: WNV human clinical cases and asymptomatic infections for selected years by report week^{figure 3 table note ±}, in Canada**

Table showing WNV human clinical cases and asymptomatic infections in Canada, by report week for selected years
Year	Report Week^{figure 3 table note ±}	Total
2018	0	1	0	0	0	0	0	0	1	5	7	15	30	54	50	35	26	9	0	-	-	-	-	-	-	-	-	-	234
2017	0	0	0	0	0	1	0	1	1	7	3	8	10	26	31	31	27	13	16	7	8	4	1	1	3	0	0	0	200
2016	0	0	0	0	1	0	0	0	0	0	1	5	5	14	11	16	12	9	6	15	5	0	0	3	1	0	1	0	105
2014	0	0	0	0	0	0	0	0	0	1	0	0	0	4	3	5	6	1	1	0	0	1	0	0	0	0	0	0	22
2012	0	0	0	1	0	0	0	3	5	11	16	27	53	63	57	43	43	45	24	30	14	9	5	1	0	0	0	0	450
2007	0	0	0	2	2	3	4	11	35	36	72	139	424	471	443	287	182	116	71	30	18	10	11	5	4	2	0	0	2,378
2003	0	0	0	0	0	0	1	1	1	5	11	9	27	66	249	323	324	178	107	82	37	14	8	4	3	0	0	0	1,450
'-' = Not available. Figure 3 table notes Figure 3 table note ± WNV clinical cases and asymptomatic infections are grouped by report week, based on episode date. Episode date could include one of the following: onset date, diagnosis date, lab sample date or reporting date. Return to figure 3 table note ± referrer

Table 1: WNV human clinical cases and asymptomatic infections in Canada by report week^{Footnote *} and year to date, 2018
Province/Territory	Clinical Cases			Total clinical cases^{table 1 note 1}	Total travel-related cases^{table 1 note 2}	Total asymptomatic infections^{table 1 note 3}
Province/Territory	Neurological syndrome	Non-neurological syndrome	Unclassified/ Unspecified	Total clinical cases^{table 1 note 1}	Total travel-related cases^{table 1 note 2}	Total asymptomatic infections^{table 1 note 3}
Report week 38: September 16 to September 22, 2018
British Columbia	0	0	0	0	0	0
Alberta	0	0	0	0	0	0
Saskatchewan^{table 1 note 4}	0	-	-	-	-	-
Manitoba	0	0	0	0	0	0
Ontario	0	0	0	0	0	0
Québec	0	0	0	0	0	0
Newfoundland and Labrador	0	0	0	0	0	0
Prince Edward Island	0	0	0	0	0	0
Nova Scotia	0	0	0	0	0	0
New Brunswick	0	0	0	0	0	0
Yukon Territory	0	0	0	0	0	0
Northwest Territory	0	0	0	0	0	0
Nunavut	0	0	0	0	0	0
Total	0	0	0	0	0	0
Year to date: January 1 to September 22, 2018
British Columbia	0	0	0	0	0	0
Alberta	5	32	0	37	7	5
Saskatchewan^{table 1 note 4}	0	-	-	-	-	-
Manitoba	3	3	23	29	0	3
Ontario	40	24	24	88	2	5
Québec	50	12	0	62	2	5
Newfoundland and Labrador	0	0	0	0	0	0
Prince Edward Island	0	0	0	0	0	0
Nova Scotia	0	0	0	0	0	0
New Brunswick	0	0	0	0	0	0
Yukon Territory	0	0	0	0	0	0
Northwest Territory	0	0	0	0	0	0
Nunavut	0	0	0	0	0	0
Total	98	71	47	216	11	18
'-' = Not available. Table 1 notes Table 1 note * WNV clinical cases and asymptomatic infections are grouped by report week, based on episode date. Episode date could include one of the following: onset date, diagnosis date, lab sample date or reporting date. Return to table 1 note * referrer Total clinical cases are the sum of confirmed and probable: WNV neurological and non-neurological syndromes, along with any unclassified or unspecified cases. Return to table 1 note 1 referrer Table 1 note 2 Likely related to travel outside the Province/Territory. These cases are included in either the total clinical cases or WNV asymptomatic infections. Return to table 1 note 2 referrer Table 1 note 3 Satisfies WNV diagnostic test criteria in the absence of clinical criteria. This category could include asymptomatic blood donors whose blood is screened using a nucleic acid amplification test, by blood operators (i.e. Canadian Blood Services or Héma-Quebec) and is subsequently brought to the attention of public health officials. Blood operators in Canada perform a supplementary WNV specific nucleic acid amplification test following any positive donor screen test result. Return to table 1 note 3 referrer Table 1 note 4 Saskatchewan provides counts of WNV neurological syndrome cases only. Return to table 1 note 4 referrer

Table 2: WNV mosquito surveillance^{table 2 note *} in Canada, as of September 22, 2018
Province / Territory	Number of positive mosquito pools	Number of mosquito pools tested	Percentage of positive mosquito pools (%)
Saskatchewan	50	761	6.57
Manitoba	168	1,924	8.73
Ontario	304	12,581	2.42
Québec	39	1,548	2.52
Total	561	16,814	3.34
Table 2 notes Table 2 note * Mosquito surveillance data is reported by the following four provinces: Saskatchewan, Manitoba, Ontario, and Québec. Return to table 2 note * referrer

Table 3: Total number of WNV mosquito pools tested by report week and by province/territory, 2018^{table 3 note ‡}
Province / Territory	Report Week																			Total
Province / Territory	22	23	24	25	26	27	28	29	30	31	32	33	34	35	36	37	38	39	40	Total
Saskatchewan	0	15	18	17	45	55	90	104	96	106	62	65	52	26	10	0	-	-	-	761
Manitoba	15	39	89	107	124	122	241	240	247	169	172	163	113	39	29	15	-	-	-	1,924
Ontario	0	0	0	0	842	955	1,024	963	1,073	1,059	1,156	1,124	1,133	998	920	667	667	-	-	12,581
Québec	0	69	77	105	105	113	109	109	110	99	123	122	102	103	122	80	-	-	-	1,548
Total	15	123	184	229	1,116	1,245	1,464	1,416	1,526	1,433	1,513	1,474	1,400	1,166	1,081	762	667	-	-	16,814
'-' = Not available. Table 3 notes Table 3 note ‡ Detailed West Nile Virus mosquito surveillance data can be accessed through provincial/territorial websites. Return to table 3 note ‡ referrer

Figure 4. Text version below. — **Figure 4: Number of WNV positive dead wild birds in Canada^{figure 4 note *} by report week^{figure 4 note ‡}, 2018**

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