West Nile Virus and Other Mosquito-borne Disease National Surveillance Report

2016 - Final - Summary West Nile Virus in Canada

Humans

During the 2016 West Nile virus (WNV) season, seven provinces (Alberta, Manitoba, Ontario, Quebec, Saskatchewan, New Brunswick and Prince Edward Island) reported West Nile virus activity to the Public Health Agency of Canada. 104 human clinical cases (both confirmed cases and probable cases) were reported in Canada: Alberta (5), Manitoba (23), Ontario (44), Quebec (30), New Brunswick (1), and Prince Edward Island (1). Of these, sixty (58%) were classified as West Nile virus Neurological Syndrome, thirty-seven (35%) as West Nile virus Non-Neurological Syndrome, and seven (7%) as unclassified. Nine fatalities were reported. In addition, two asymptomatic infections were reported: one in Manitoba, and the other in Saskatchewan.

Mosquitoes

345 (2.28 %) out of 15,124 mosquito pools tested positive for West Nile virus in the following provinces: Saskatchewan 67 (11.22%), Manitoba 39 (2.80 %), Ontario 211 (1.73 %), and Quebec 28 (2.99%).

Wild Birds

The Canadian Wildlife Health Cooperative and the Québec Centre for Wild Animal Health examined a total of 141 dead birds for WNV in 2016, of which 37 (26%) dead birds were positive for West Nile virus: British Columbia (2), Saskatchewan (4), Ontario (20), and Quebec (11).

The positive bird species included Red-tailed hawk (29%), American crow (24%), Sharp -shinned hawk (16%), Merlin (8%), Goshawk (8%), Black-billed Magpie (3%), Blue Jay (3%), Burrowing Owl (3%), Cooper’s Hawk (3%), and Great horned owl (3%).

Domestic Animals

Forty-six horses with WNV infection were reported to the Canadian Food Inspection Agency by various provincial/private animal health laboratories. In addition, the Quebec Ministry of Agriculture, Fisheries and Food, reported two horses positive for West Nile virus.

Ten horses were reported in British Columbia [Langley(1), Nelson (1), Cranbrook (4) and Creston (4)], seven in Alberta [ Lethbridge (3), Taber (1), Brooks (1), Dalemead (1), Strathmore (1)], thirteen in Manitoba [Minnedosa (1), Steinbach (2), Winnipeg (1), Beauséjour (1), Hartney (3), Stonewall (1), Virden (2), Glenboro (1), Elm Creek (1) ], thirteen in Saskatchewan [ Maple Creek (3), Moose Jaw (2), Ogema (1), Swift Current (2), Redvers (1), Assiniboia (1), Melfort (1), Saskatoon (1), Simmie (1) ], two in Ontario [ Mississauga (1), Denfield (1)], and three in Quebec [ Saint-Hyacinthe (1), Lanaudiere (1), Mauricie-Centre du Quebec (1) ].

Eastern Equine Encephalitis Virus in Canada

Humans

In the summer 2016, the first human case of mosquito-borne Eastern Equine Encephalitis (EEE) virus was reported in Canada. The individual was a resident of Ontario and has fully recovered.

Domestic Animals

Two horses tested positive for Eastern Equine Encephalitis virus in Quebec and were reported by the Canadian Food Inspection Agency through various private animal health laboratories.

California Serogroup Viruses in Canada

In 2016, 24 human cases of laboratory confirmed cases/exposures of California serogroup virus were diagnosed by the National Microbiology Laboratory in the following provinces: Alberta (3), Manitoba (3), Ontario (2), Quebec (11), New Brunswick (2), and Nova Scotia (3). Of these cases, 14 were further classified as Jamestown Canyon virus, 3 as Snowshoe hare virus, and the rest as unknown. Most of the samples were initially collected for testing West Nile virus, and further assayed for non-West Nile virus mosquito-borne agents.

Figure 1: Geographic distribution of West Nile virus in humans (clinical cases) and horses in Canada, 2016


Figure 2: West Nile virus clinical cases and asymptomatic infections by Province/ Territory, Canada, 2016

 

*     West Nile virus 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

Table 1: West Nile virus human clinical cases and asymptomatic infections, by Province/ Territory and by report week, 2016 seasonFootnote *
Province Episode weeks/ month, 2016
Apr May June July Aug Sept Oct Nov Dec
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
Table 1 Footnote *

West Nile virus 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 first Table 1 footnote * referrer

Prince Edward Island 0 0 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 0 0 0
New Brunswick 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Quebec 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 2 3 1 3 11 4 0 0 2 1 0 1 0 0 0 0
Ontario 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 3 5 6 10 6 6 2 3 0 0 0 0 0 0 0 0 0 0 0
Manitoba 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 2 7 4 2 2 2 1 1 1 0 0 0 0 0 0 0 0 0 0
Saskatchewan 0 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 0 0 0 0
Alberta 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 2 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0
Total 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
Table 2: West Nile virus human clinical cases and asymptomatic infections by Province/ Territory for the 2016 season
Province West Nile virus neurological syndrome West Nile virus non-neurological syndrome Unclassified/ unspecified Total clinical casesFootnote 1 Number of travel-related casesFootnote 2 West Nile virus asymptomatic infectionFootnote 3
Table 2 Footnote 1

Total clinical case 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 first Table 2 footnote 1 referrer

Table 2 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 first Table 2 footnote 2 referrer

Table 2 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 first Table 2 footnote 3 referrer

Table 3 Footnote *

One of these cases was likely exposed prior to the 2016 West Nile virus season.

Return to first Table 2 footnote * referrer

Prince Edward Island 0 1 0 1 1 0
New Brunswick 0 1 0 1 1 0
Quebec 18Footnote * 12 0 30Footnote * 0 0
Ontario 29 8 7 44 2 0
Manitoba 12 11 0 23 0 1
Saskatchewan 0 0 0 0 0 1
Alberta 1 4 0 5 1 0
Total 60 37 7 104 5 2

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

*     West Nile virus 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.

Table 3: West Nile virus clinical cases and asymptomatic infections by report week for selected years
Year Episode weeks/month, 2016
Apr May June July Aug Sept Oct Nov Dec
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
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
2015 1 0 0 0 0 1 0 1 2 1 0 0 1 1 3 4 7 6 6 5 13 11 8 8 2 3 0 0 0 0 0 0 0 0
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
2013 0 0 0 0 0 1 1 0 0 0 1 2 2 5 5 6 9 10 21 16 14 12 7 2 1 0 1 1 0 0 0 0 0 1
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
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
2005 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4 4 11 28 28 38 45 27 15 7 12 3 3 1 0 0 0 0 0 0
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
Table 4: Number of mosquito pools tested for West Nile virus and number of positive mosquito pools by Province/ Territory, 2016 season
Province 2016 West Nile virus seasonFootnote *
Number of positive mosquito pools Number of mosquito pools tested Percentage of positive mosquito pools (%)
Table 4 Footnote *

In 2016, mosquito surveillance was conducted by the following provinces only: Quebec, Ontario, Manitoba and Saskatchewan

Return to first Table 4 footnote * referrer

Quebec 28 935 2.99
Ontario 211 12198 1.73
Manitoba 39 1394 2.80
Saskatchewan 67 597 11.22
Total 345 15124 2.28
Table 5: Reported number of dead birds tested positive for West Nile virus by Province/ Territory and by report week, 2016 seasonFootnote *
Province Report Weeks of 2016
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
Table 5 Footnote *

Data from the Canadian Wildlife Health Cooperative and the Québec Centre for Wild Animal Health

Return to first Table 5 footnote * referrer

Quebec 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 3 1 2 2 0 1 1 0 0 0 0 0
Ontario 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 3 0 0 1 2 0 4 0 8 0 0 0
Saskatchewan 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 2 0 1 0 0 0 0 0 0 0
British Columbia 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
Total 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 3 7 1 4 3 3 1 5 0 8 0 0 0

Figure 4:     Numbers and Percentages of dead birds tested positive for West Nile virus in the 2016 season by report week, as compared to percentages in 2003, 2012 and 2015 seasons

Table 6: Numbers and Percentages of dead birds tested positive for West Nile virus in the 2016 season by report week, as compared to percentages in 2003, 2012 and 2015 seasons
  Year Report Weeks
1  to 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
Numbers positive 2016 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 3 7 1 4 3 3 1 5 0 8 0 0 0 0 0 0 0
Numbers tested 2016 4 1 0 0 1 4 3 1 3 1 2 5 9 4 2 6 6 30 4 5 7 7 5 14 3 10 1 1 1 0 0 0 1
Percentage positive 2016 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
Percentage positive 2015 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
Percentage positive 2012 0 0 0 0 0 0 0 0 0 0 33 67 33 67 33 50 67 64 67 33 67 67 55 0 0 0 0 0 0 0 0 0 0
Percentage positive 2003 0 0 1 0 1 1 1 1 1 3 3 6 7 10 17 21 38 35 43 46 45 45 58 29 20 15 8 0 0 0 0 0 0

Figure 5: Geographic distribution of Eastern Equine Encephalitis in horses in Canada, 2016

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