2008 Surveillance for West Nile virus in Manitoba
2008 Positive Surveillance Indicators*
Surveillance Indicator 2008 2007 2006 2005 2004 2003 2002
Corvids 1 __ __ __ 12 16 134 86
Mosquito Collections (Adult)
41
 948 171 193 57 290 15
Horse Cases
0
 8 1 4 0 47 236
Human Cases (Total) 2
12
 587 51 58 3 143 0

* As of November 6, 2008.

1 The West Nile virus dead corvid pick up program is not in effect in 2008. Dead corvids are no longer needed as an early indicator of West Nile virus in Manitoba or to determine geographic distribution. Larval sampling, mosquito sampling and testing in addition to other factors (temperature, etc.) will be used to guide the assessment of risk of West Nile virus exposure.

2Additional information on these cases including classification, age, gender, regional health authority of residence and likeliest area of exposure is available here.

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Culex tarsalis Mosquito Trap Catch by Regional Health Authority*
Average Adult Culex tarsalis Mosquitoes per Weekly Trap Catch
Regional Health Authority May 18-24 May 25-31 June 1-7
Assiniboine 0 0 0
Brandon 0 0 0
Central 0 0 0
Interlake 0 0 0
North Eastman 0 0 0
Parkland 0 0 0
South Eastman 0 0 0
Winnipeg 0 0 0
Manitoba 0 0 0
 
Regional Health Authority June 8-14 June 15-21 June 22-28
Assiniboine <1 <1 <1
Brandon 0 0 <1
Central 0 0 0
Interlake 0 0 0
North Eastman 0 0 0
Parkland 0 0 <1
South Eastman 0 0 0
Winnipeg 0 0 <1
Manitoba <1 <1 <1
 
Regional Health Authority June 29-July 5 July 6-July 12 July 13-July 19
Assiniboine 5
40
58
Brandon 2
2
13
Central 0
<1
4
Interlake <1
<1
3
North Eastman <1
<1
1
Parkland 0
3
4
South Eastman 0
<1
3
Winnipeg <1
<1
4
Manitoba 1 9
17
 
Regional Health Authority July 20-July 26 July 27-August 2 August 3-August 9
Assiniboine
105
373
613
Brandon
9
13
58
Central
7
45
26
Interlake
9
23
118
North Eastman
5
7
23
Parkland
11
38
24
South Eastman
11
8
11
Winnipeg
4
12
34
Manitoba
29
103
176
 
Regional Health Authority August 10-August 16 August 17-August 23 August 24-August 30
Assiniboine
766
657
46
Brandon
191
74
29
Central
53
63
3
Interlake
90
90
13
North Eastman
12
15
2
Parkland
209
38
<1
South Eastman
16
39
3
Winnipeg
61
119
27
Manitoba
239
209
21
 
Regional Health Authority August 31-September 6 September 7 - September 13  
Assiniboine
11
<1
Brandon
<1
0
Central
4
0
Interlake
6
0
North Eastman
4
<1
Parkland
<1
0
South Eastman
4
0
Winnipeg
16
<1
Manitoba
8
<1

* As of October 15, 2008.
(Routine mosquito trapping was discontinued the week ending September 13, 2008.)

Permanent mosquito traps are set up in 37 community areas in southern Manitoba to monitor Culex tarsalis mosquitoes, the mosquitoes that are most likely to transmit West Nile virus to humans in Manitoba. The above table will represent the average number of Culex tarsalis mosquitoes per trap catch for the week by Regional Health Authority (RHA) and  provides a relative measure of the activity levels of Culex tarsalis from one RHA to another and over time. This measure is an indicator as to whether Culex tarsalis mosquito populations are rising or falling or staying steady. It should be noted that these RHA averages provide an approximate indication of the number of Culex tarsalis in the RHA, counts in specific locations within the RHA will vary depending on local conditions, temperature, precipitation, etc.

Note:  Normally, two Centers for Disease Control (CDC) mosquito traps baited with carbon dioxide are run for two nights each week in each Manitoba community except Winnipeg and Brandon (where proportionately more traps are used because of larger community size). 

The average number of Culex tarsalis per trap catch (a trap catch – may also be called a “collection”- represents the mosquitoes collected by one trap during one night from approximately one hour before sunset until approximately one hour after sunrise) is calculated by dividing the total number of Culex tarsalis collected for the whole week in a given RHA by the number of collections.

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Positive Mosquito Collections (Adult) by RHA*
Positive Mosquito Collections (Adult) by RHA 2008
Assiniboine
30
Brandon
4
Central
0
Interlake
3
North Eastman
1
Parkland
0
South Eastman
0
Winnipeg
3
Total 41

* As of October 15, 2008
(Routine mosquito trapping was discontinued the week ending September 13, 2008.)

Mosquito samples from the following communities have tested positive for WNV in 2008: Beausejour, Boissevain, Brandon, Carberry, Deloraine, East St. Paul, Killarney, Selkirk, Sioux Valley First Nation, Stonewall, Virden, West St. Paul and Winnipeg.

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WNV Human Cases by Regional Health Authority*

Represents the Regional Health Authority of residence of the patient.

Regional
Health
Authority		 Asymptomatic West Nile Virus Non-Neurological Syndrome West Nile Virus
Neurological Syndrome		 Unclassified Positive
Test
Results		 TOTAL
Assiniboine
0
2
1
0
3
Brandon
0
1
0
0
1
Central
0
0
0
0
0
Interlake
0
2
1
0
3
NorMan
0
0
0
1
1
North Eastman
0
0
0
0
0
Parkland
0
0
0
0
0
South Eastman
0
1
0
0
1
Winnipeg
0
3
0
0
3
Total
0
9
2
1
12 ^
Out of Province
0
0
0
1
1 1

^ 2 cases tested positive for West Nile virus in the 2008 WNV season and through further investigation were determined to have been exposed to West Nile virus in a previous season and are not included in Manitoba’s 2008 total case counts

1 Positive test results of West Nile virus identified in non-Manitoba residents are not counted in Manitoba’s total case counts and are counted by the jurisdiction of residence.

The most likely locations of exposure have been determined for at least one human case in each of the following municipalities: RM of Armstrong, RM of Park (South), RM of Roblin, RM of South Cypress, Town of Melita, Town of Minnedosa and the Town of Stonewall. Further information on most likely locations of exposure will be added as it becomes available.

Note: 2008 human case classifications include both final and preliminary classifications and may be subject to change as further information becomes available.

* As of November 6, 2008.

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Severity of WNV Disease By Age*
Age in Years Asymptomatic West Nile Virus Non-Neurological Syndrome West Nile Virus
Neurological Syndrome		 Unclassified Positive
Test
Results		 Total
  0 -   9
0
0
0
0
0
10 - 19
0
2
0
0
2
20 - 29
0
4
0
0
4
30 - 39
0
1
0
0
1
40 - 49
0
1
0
0
1
50 - 59
0
1
0
1
2
60 - 69
0
0
1
0
1
Over 70
0
0
1
0
1
Total
0
9
2
1
12

* As of November 6, 2008.

Average Age - West Nile Virus Non Neurological Syndrome: 28
Average Age - West Nile Virus Neurological Syndrome: 75

Note: 2008 human case classifications include both final and preliminary classifications and may be subject to change as further information becomes available.

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WNV Disease by Gender*
Gender Asymptomatic West Nile Virus Non-Neurological Syndrome West Nile Virus
Neurological Syndrome		 Unclassified Positive
Test
Results		 Total
Male
0
3
2
1
6
Female
0
6
0
0
6
Total
0
9
2
1
12

* As of November 6, 2008.

Note: 2008 human case classifications include both final and preliminary classifications and may be subject to change as further information becomes available.

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Additional information and maps are available at the Public Health Agency of Canada website.

For WNV health concerns, contact your doctor or call:

Health Links - Info Santé
204-788-8200 (Winnipeg) or toll-free 1-888-315-9257