2008 Surveillance for West Nile virus in Manitoba

• Positive Surveillance Indicators
• Culex tarsalis Mosquito Trap Catch by Regional Health Authority
• Positive Mosquito Collections (Adult) by RHA
• WNV Patients by Regional Health Authority
• Severity of WNV Disease by Age
• WNV Disease by Gender

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Positive Surveillance Indicators*

Surveillance Indicator	2008	2007	2006	2005	2004	2003	2002
Corvids 1	__	__	__	12	16	134	86
Mosquito Collections (Adult)	0	948	171	193	57	290	15
Horse Cases	0	8	1	4	0	47	236
Human Cases (Classified)	0	582	51	58	3	143	0

* As of July 3, 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.

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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

* As of July 3, 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	0
Brandon	0
Central	0
Interlake	0
North Eastman	0
Parkland	0
South Eastman	0
Winnipeg	0
Total	0

* As of July 3, 2008.

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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	0	0	0	0
Brandon	0	0	0	0	0
Central	0	0	0	0	0
Interlake	0	0	0	0	0
North Eastman	0	0	0	0	0
Parkland	0	0	0	0	0
South Eastman	0	0	0	0	0
Winnipeg	0	0	0	0	0
Total	0	0	0	0	0
Out of Province	0	0	0	0	0

* As of July 3, 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	0	0	0	0
20 - 29	0	0	0	0	0
30 - 39	0	0	0	0	0
40 - 49	0	0	0	0	0
50 - 59	0	0	0	0	0
60 - 69	0	0	0	0	0
Over 70	0	0	0	0	0
Total	0	0	0	0	0

* As of July 3, 2008.

Average Age - Asymptomatic West Nile Virus:
Average Age - West Nile Virus Non Neurological Syndrome:
Average Age - West Nile Virus Neurological Syndrome:

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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	0	0	0	0
Female	0	0	0	0	0
Total	0	0	0	0	0

* As of July 3, 2008.

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