2023 Surveillance Data for West Nile virus in Manitoba
Positive West Nile virus (WNV) Surveillance Indicators*
Surveillance Indicators** 2023 2022 2021 Historical Maximum
WNV Positive Mosquito Collections (Adults) 48 33 110 948
Human Cases (Total)*** 2 3 5 588

* As of September 3, 2023

** 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 28 – June 3
0
No trapping
0
0
0
June 4 - 10 < 1 3 3 3 3
June 11 - 17 < 1 < 1 2 1 1
June 18 - 24 6 > 1 11 12 9
June 25 - July 1 11 2 13 10 10
July 2 - July 8 6 28 25 10 17
July 9 - July 15 2 8 10 3 6
July 16 - July 22 1 3 14 1 6
July 23 - July 29 3 6 15 6 8
July 30 - August 5 4 18 16 12 12
August 6 - August 12 4 17 24 15 16
August 13 - August 19 1 8 10 5 7
August 20 - August 26 < 1 < 1 2 3 2
August 27 - Sept 2 < 1 < 1 < 1 < 1 < 1
Sept 3 - Sept 9 < 1 < 1 < 1 < 1 < 1

* As of September 3, 2023

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
2

Prairie Mountain
8

Southern-Santé Sud
28

Winnipeg
10
Total
48

* As of September 3, 2023

** As of September 9, 2023: Positive pools were detected in the communities of Altona, Brandon, Boissevain, Killarney, Morden, Morris, Oakbank, Portage, Selkirk, Steinbach, 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
0
0
2
1
3
Confirmed
0
1
0
1
2
Total
0
1
2
2
5

* As of September 3, 2023

** 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
0
1
4
0
5

* As of September 3, 2023

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