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West Nile virus and other mosquito-borne diseases national surveillance report — October 8 to October 14, 2017 (Week 41)

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West Nile Virus

Canada

Humans

During week 41, October 8 to October 14, 2017, no new cases of West Nile Virus (WNV) were reported to the Public Health Agency of Canada (PHAC). Retrospectively, seven additional cases were reported by three provinces: two in Québec, four in Ontario and one in Manitoba.

As of week 41, 166 clinical cases and six asymptomatic infections have been reported to the PHAC by five provinces (Québec [15], Ontario [147], Manitoba [4], Alberta [5], and British Columbia [1]). Of the 166 clinical cases, fifty-seven (34%) were classified as WNV neurological syndrome, fifty-four (33%) as WNV Non-neurological syndrome, and thirty-three (33%) as unclassified. A total of 21 travel-related cases were reported. As of October 14, six deaths associated with West Nile virus have been reported to the Public Health Agency of Canada during the 2017 season.

Mosquitoes

As of initial surveillance, 17,374 mosquito pools have been tested for WNV in Canada: Québec (1,849), Ontario (14,076), Manitoba (1,028), and Saskatchewan (421).

A total of 544 positive pools of WNV have been found in the following four provinces: 409 in Ontario [Brant County (2), Chatham-Kent (3), Durham Region (10), Eastern Ontario (5), Halton Region (36), Hamilton (31), Haliburton-Kwartha-Pine Ridge District (1), Hastings and Prince Edward Countries (13), Huron County (2), Kingston-Frontenac and Lennox and Addington (5), Lambton (2), Leeds, Grenville and Lanark District Health Unit (1), Middlesex-London (7), Niagara Region (15), Northwestern (1), Ottawa (35), Oxford County (1), Peel (114), Perth District (6), Peterborough County-City (2), Renfrew County and District (2), Simcoe Muskoka District (2), Toronto (62), Waterloo (3), Wellington-Dufferin-Guelph (3), Windsor-Essex County (29), and York Regional (16)]; forty-one in Manitoba[(Winnipeg (13), Southern (5), Interlake Eastern (7), and Prairie Mountain (16)]; eighty-four in Québec [Capitale-Nationale (9), Mauricie et du Centre-du-Québec (6), Montréal (10), Outaouais (3), Laval (5), Lanaudière (9), Laurentides (42)]; and ten in Saskatchewan.

Birds

As of week 41, the Canadian Wildlife Health Cooperative has tested 192 dead birds for WNV (Northwest Territories [1], Prince Edward Island [1], Quebec [105], Ontario [64], Saskatchewan [16], Manitoba [2], Alberta [1], and British Columbia [2]). Of these, 130 were positive: eighty in Quebec, two in Manitoba, thirty-eight in Ontario, and ten in Saskatchewan.

Domestic Animals

The Canadian Food Inspection Agency has reported forty-nine horses with WNV infection in the following six provinces: Québec (7), Ontario (19), Manitoba (1), Saskatchewan (8), Alberta (10), and British Columbia (4). 

United States and U.S. territories

As of October 17, 2017, 1,502 human cases of WNV have been reported by the Centers for Disease Control and Prevention. Of these, 987 (66%) were classified as neuroinvasive disease and 515 (34%) as non-neuroinvasive disease. Eighty-six deaths have been reported during the season. In addition, 202 presumptive viremic blood donors have been identified.

Detailed information can be accessed via the CDC web site.

Europe and Neighbouring Countries

As of October 13, 2017, the European Centre for Disease Prevention and Control reported a total of 252 (confirmed and probable) cases of West Nile fever [Austria (4), Bulgaria (1), Croatia (5), Greece (47), Hungary (19), Israel (17), Italy (53), Romania (60), and Serbia (46)].

Detailed information can be accessed via the ECDC web site.

Other Mosquito-borne Diseases

Canada

Eastern Equine Encephalitis virus

No human cases of eastern equine encephalitis virus (EEEV) have been reported to the Public Health Agency of Canada in 2017. There have been no reports of horses testing positive for EEEV; however, there has been one horse reported with eastern equine encephalitis virus, from Ontario.

California Serogroup virus

Since January 1, 2017, 45 human cases of laboratory-confirmed cases/exposures of California serogroup virus were diagnosed by the National Microbiology Laboratory in Canada: British Columbia (1), Alberta (5), Saskatchewan (5), Manitoba (1), Ontario (1), Quebec (27), New Brunswick (3) and Nova Scotia (2).  Of these cases, twenty-seven were further classified as Jamestown Canyon virus and one Snowshoe hare virus.

Figure 1: Geographic distribution of WNV human cases in Canada, as of October 14, 2017

Figure 1 text equivalent

Map showing geographic distribution of human cases of WNV in Canada.

As of surveillance week 41, ending October 14, 2017, there are 172 human cases of WNV in Canada; fifteen from Québec, 147 from Ontario, four from Manitoba, five from Alberta, and one from British Columbia.

Figure 2: West Nile virus human clinical cases and asymptomatic infections by province/territory and by report week, as of October 14, 2017

Figure 2 Footnote 1

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 footnote * referrer

Figure 2 text equivalent

As of week 41, ending October 14, 2017, there are 172 human clinical cases and asymptomatic infections associated with WNV in Canada.

Table showing human clinical cases and asymptomatic infections associated with WNV in Canada, by province or territory and by week monitoring, dated 14 October 2017
  Report Week Figure 2 Footnote * Total
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45
British Columbia 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1
Ontario 0 0 0 0 0 0 0 1 0 1 1 7 3 6 5 17 14 30 22 6 17 10 5 2 0 0 0 0 0 147
Alberta 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4 0 1 0 0 0 0 0 0 0 0 0 0 5
Manitoba 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0 1 0 0 0 0 0 0 0 0 0 0 4
Québec 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2 2 4 1 1 2 0 1 0 0 0 0 0 0 0 15
Total 0 0 0 0 0 0 0 1 0 1 1 7 3 8 7 20 25 31 25 8 17 11 5 2 0 0 0 0 0 172

Figure 3: West Nile virus human clinical cases and asymptomatic infections by report week for selected years, in Canada

Figure 3 Footnote 1

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 footnote * referrer

Figure 3 text equivalent
Table showing WNV human clinical cases and asymptomatic infections in Canada, by report week for selected years
  Report Week Figure 3 Footnote * Total
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
2017 0 0 0 0 0 0 0 1 0 0 1 7 3 8 7 20 25 31 25 8 17 11 5 2 0 0 0 0 0 0 0 0 0 0 172
2016 0 0 0 1 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 0 0 0 106
2014 0 0 0 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 0 0 0 22
2012 0 0 0 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 0 0 0 450
2007 0 0 0 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 0 0 0 2,378
2003 0 0 0 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 0 0 0 1,450
Table 1: West Nile virus human clinical cases and asymptomatic infections by province/territory for the current report week and year to date, 2017 season
Province/Territory Week 41: October 8 to October 14, 2017
WNV Cases Total clinical casesTable 1 Footnote 1 # of travel related WNV casesTable 1 Footnote 2 # of asymptomatic WNV infectionsTable 1 Footnote 3
Neurological syndrome Non-Neurological syndrome Unclassified / Unspecified
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
Québec 0 0 0 0 0 0
Ontario 0 0 0 0 0 0
Manitoba 0 0 0 0 0 0
SaskatchewanTable 1 Footnote 4 0 - - - - -
Alberta 0 0 0 0 0 0
British Columbia 0 0 0 0 0 0
Yukon Territory 0 0 0 0 0 0
Northwest Territories 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 October 14, 2017
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
Québec 12 2 0 14 0 1
Ontario 41 47 55 143 20 4
Manitoba 2 2 0 4 0 0
SaskatchewanTable 1 Footnote 4 0 - - - - -
Alberta 2 3 0 5 1 0
British Columbia 0 0 0 0 0 1
Yukon Territory 0 0 0 0 0 0
Northwest Territories 0 0 0 0 0 0
Nunavut 0 0 0 0 0 0
Total 57 54 55 166 21 6
Table 1 Footnote 1

Total clinical cases is the sum of both probable and confirmed: West Nile virus neurological and non-neurological syndromes, along with any unclassified or unspecified cases.

Return to table 1 footnote 1 referrer

Table 1 Footnote 2

Likely related to travel outside the Province/Territory. These cases are included in either the total clinical cases or West Nile virus asymptomatic infections.

Return to table 1 footnote 2 referrer

Table 1 Footnote 3

Satisfies West Nile virus 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 Hema-Quebec) and is subsequently brought to the attention of public health officials. Blood operators in Canada perform a supplementary West Nile virus specific nucleic acid amplification test following any positive donor screen test result.

Return to table 1 footnote 3 referrer

Table 1 Footnote 4

Saskatchewan provides counts of WNV neurological syndrome cases only.

Return to table 1 footnote 4 referrer
Table 2: Number of mosquito pools tested for West Nile virus and number of positive mosquito pools by province/territory, 2017 season
Province/Territory Year to date: January 1 to October 14, 2017
Number of positive mosquito pools Number of mosquito pools tested Percentage of positive mosquito pools (%)
Quebec 84 1,849 4.54
Ontario 409 14,076 2.91
Manitoba 41 1,028 3.99
Saskatchewan 10 421 2.38
Alberta - - -
British Columbia - - -
Newfoundland and Labrador - - -
Prince Edward Island - - -
Nova Scotia - - -
New Brunswick - - -
Yukon Territory - - -
Northwest Territory - - -
Nunavut - - -
Total 544 17,374 3.13
Table 3: Total number of WNV mosquito pools tested by report week and by province/ territory, 2017 seasonTable 3 Footnote 1
Province / Territory Report week of 2017 Total
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41
Québec - - - - - - - - 147 147 147 147 147 147 147 146 147 147 147 122 122 0 0 1,849
Ontario 13 15 43 84 194 299 718 794 964 1,003 1,037 1,053 1,168 1,015 1,116 993 931 746 634 523 523 91 1 14,076
Manitoba - - - - 15 45 48 16 60 93 96 113 178   122 86 104 25 20 7 -     1,028
Saskatchewan - - - - 6 20 11 18 25 31 38 46 61 52 39 40 34 - - -       421
Alberta - - - - - - - - - - - - - - - - - - - -       0
British Columbia - - - - - - - - - - - - - - - - - - - -       0
Newfoundland and Labrador - - - - - - - - - - - - - - - - - - - -       0
Prince Edward Island - - - - - - - - - - - - - - - - - - - -       0
Nova Scotia - - - - - - - - - - - - - - - - - - - -       0
New Brunswick - - - - - - - - - - - - - - - - - - - -       0
Yukon Territory - - - - - - - - - - - - - - - - - - - -       0
Northwest Territories - - - - - - - - - - - - - - - - - - - -       0
Nunavut - - - - - - - - - - - - - - - - - - - -       0
Total 13 15 43 84 215 364 777 828 1,196 1,274 1,318 1,359 1,554 1,336 1,388 1,283 1,137 913 788 752 645 91 1 17,374
Table 3 Footnote 1

Detailed West Nile virus mosquito surveillance data can be accessed through Provincial/ Territorial websites

Return to table 3 footnote 1 referrer

Figure 4: Reported number of dead birds tested positive for WNV by province/territory and by report week, 2017 season in CanadaFigure 4 Footnote

Figure 4 Footnote 1

Not all provinces are conducting dead bird surveillance as part of their own WNV surveillance program. However, WNV positive dead birds may be identified through the National Wildlife Disease Surveillance Program of the Canadian Wildlife Health Cooperative.

Return to figure 4 footnote referrer

Figure 4 text equivalent

As of week 41, ending October 14 in 2017, there are 130 WNV cases in birds, in Canada.

Table showing the reported number of dead birds tested positive for WNV in Canada, by province/territory and by report week, 2017 season.
Report Week
  14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 Total
Manitoba 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2
Ontario 0 0 1 0 0 0 0 0 0 0 0 3 1 1 0 0 2 5 1 7 4 3 5 1 0 2 1 1 0 0 0 0 0 0 0 0 0 38
Québec 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5 3 9 10 7 8 10 15 6 2 3 2 0 0 0 0 0 0 0 0 0 0 0 80
Saskatchewan 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 4 3 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 10
Total 0 0 1 0 0 0 0 0 0 0 0 3 1 1 5 3 13 16 8 19 17 19 12 3 3 4 1 1 0 0 0 0 0 0 0 0 0 130

Figure 5: Percentage of dead birds tested positive for WNV by report week in 2012, 2015, 2016, 2017 and number of dead birds tested positive, by report week, 2017, in CanadaFigure 5 Footnote

Figure 5 Footnote 1

Not all provinces are conducting dead bird surveillance as part of their own WNV surveillance program. However, WNV positive dead birds may be identified through the National Wildlife Disease Surveillance Program of the Canadian Wildlife Health Cooperative.

Return to figure 5 footnote referrer

Figure 5 text equivalent
Table showing percentage of dead birds tested positive for WNV in Canada by report week in 2012, 2015, 2016 and 2017 and the number of dead birds that tested positive for WNV by report week, 2017 season
  Report Weeks Total
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49
2013 Percentage positive 0 0 0 0 0 0 0 0 0 20 0 0 56 20 45 47 38 38 75 69 67 60 67 0 50 100 0 17 0 0 0 0 0 43.5%
2014 Percentage positive 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 15 20 29 31 0 27 75 0 20 0 50 0 0 0 0 0 0 0 20.4%
2015 Percentage positive 0 0 0 0 0 0 0 100 0 0 0 100 83 60 73 0 25 67 83 57 50 80 67 0 21 0 0 0 0 50 0 0 0 51.0%
2016 Percentage positive 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 33 50 23 25 80 43 43 20 36 0 80 0 0 0 0 0 0 0 26.2%
2017 Percentage positive - 0 0 0 0 0 0 0 100 33 50 100 33 87 84 57 76 74 90 86 60 60 36 33 100                  
2017 Number positive - 0 0 0 0 0 0 0 3 1 1 5 3 13 16 8 19 17 19 12 3 3 4 1 1                 130

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