2021 Surveillance Data for West Nile virus in Manitoba
Positive West Nile virus (WNV) Surveillance Indicators*
Surveillance Indicators** 2021 2020 2019 Historical Maximum
WNV Positive Mosquito Collections (Adults) 110 3 7 943
Human Cases (Total)*** 5 0 1 540

* As of September 10, 2021

** The historical comparison data is based on the same period of time for each year represented in the table above.

*** Additional information on these cases including classification, severity and health region of residence is available here.

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Culex Tarsalis Mosquito Trap Catch by Health Region
Trapping Week Health Region Manitoba
Interlake-Eastern Prairie Mountain Southern-Santé Sud Winnipeg

May 30 – June 5
<1
No trapping
<1
<1
<1
June 6 – June 12 1 No trapping 1 1 1
June 13 – June 19 3 1 10 12 8
June 20 – June 26 5 1 4 4 3
June 27 – July 3 11 13 9 8 10
July 4 – July 10 12 42 20 16 21
July 11 – July 17 14 41 40 25 31
July 18 – July 24 28 79 36 28 39
July 25 – July 31 56 83 97 141 100
August 1 – August 7 30 61 117 99 87
August 8 – August 14 14 81 35 26 36
August 15 – August 21 10 23 19 33 22
August 22 – August 28 1 1 1 1 1
August 29 – Sept. 4 <1 <1 2 1 1

* As of September 10, 2021

Permanent mosquito traps are set up in 21 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 Cx. tarsalis mosquitoes per trap catch for the week by health region and provides a relative measure of the activity levels of Cx. tarsalis from one region to another and over time. This measure is an indicator as to whether Cx. tarsalis mosquito populations are rising or falling or staying steady. It should be noted that these health region averages provide an approximate indication of the number of Cx. tarsalis in the health region, counts in specific locations within the health region 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 health region by the number of collections.

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Positive Mosquito Collections (Adult) by Health Region
Positive Mosquito Collections (Adult) by Health Region

Interlake- Eastern

10

Prairie Mountain

17

Southern-Santé Sud

38

Winnipeg

45
Total
110

* As of September 10, 2021

Note: Positive pools have been detected in the communities of Altona, Beausejour, Boissevain, Brandon, Carman, East St Paul, Morris, Niverville, Oakbank, Portage la Prairie, Ste. Anne, Selkirk, Stonewall, West St Paul, Winkler and Winnipeg.

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WNV Human Cases by Health Region*
Classification
Health Region**
 Total
Interlake-Eastern
Prairie Mountain
Southern-Santé Sud
Winnipeg
Probable

2

0

0

0

2
Confirmed

0

1

1

2

4
Total
2
1
1
2
6

* As of October 8, 2021

** Based on region of residence. Note that region of residence may not correspond to region of likely exposure.

Note:  Subject to change as further information becomes available.

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Severity of WNV Human Cases
 
Asymptomatic
West Nile Virus
Non-Neurological Syndrome
West Nile Virus Neurological Syndrome
Under
Investigation
Total
Human Cases
1
3
2
0
6

* As of October 8, 2021

Note:  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