West Nile Virus Surveillance Summary #10

Feb. 10, 2010, 10:36 a.m.

West Nile Virus Surveillance Summary #10

WNV Activity in BC

(Data as of September 23, 2009) 

Two horses have been reported positive for WNV, one horse was located in the southern Okanagan, and the other was located in the Fraser Valley.  Neither horse traveled outside the province.  This was the first positive indicator reported in the Fraser Health Authority.   One additional mosquito pool in the Southern Okanagan was also confirmed as positive.  To date there have been 2 human cases, two horses and 10 mosquito pools confirmed with WNV in BC. 

The BCCDC webpage on West Nile can be viewed directly at: http://www.bccdc.ca/dis-cond/a-z/_w/WestNileVirus/default.htm  

From June 1 st , 2009

Humans*

Corvids submitted

Corvids sighted

Mosquito pools

Horses

# Tested

313

137

387

2449

-

# Positive

2

0

 

10

2

*includes routine screening of CSF, organ and stem cell donations in addition to physician test requests 

Maps and graphs of BC surveillance data can be found at: http://www.bccdc.ca/dis-cond/a-z/_w/WestNileVirus/Surveillance/WNv2009SurveillanceData.htm  

7-day Environment Canada weather forecast for select BC communities

Warm and dry conditions are forecasted for BC over the next week. Abbotsford, Vancouver and Victoria are expecting sun and temperatures ranging 22-7oC (daily high and low, respectively). Osoyoos, Kamloops, Creston and Cranbrook are expecting sun and temperatures ranging 27-2oC.   

Accumulated base 16 o C growing degree days comparison for select BC communities

  August 31 st

2009

2008

2007

2006

2005

2004

2003

30YR

  Cranbrook

368

366

442

423

307

360

476

276

  Creston

519

414

607

554

446

517

620

351

  Osoyoos

750

649

687

687

680

809

786

540

  Kamloops

696

580

579

657

575

704

662

475

  Abbotsford

385

280

295

342

340

430

360

222

  Vancouver

289

204

221

239

245

329

275

170

  Victoria

255

189

207

237

239

296

263

153

  Prince George

252

185

189

237

184

264

196

139

 

All communities experienced dramatically increased accumulated degree days this year compared to last year and the 30 year average.  Degree day calculations beyond August 31st are not calculated as newly hatched mosquitoes have entered diapause by this time (a state where they do not seek a blood meal); therefore, the effect of temperature on mosquito development and viral replication after this time does not contribute to WNV risk.

 

WNV Activity in Canada

(Data as of September 12, 2009) 

One new human case has been reported from Saskatchewan and Alberta, both cases were classified as non-neurological syndrome.  Additionally, Ontario reported their first positive mosquito pools. 

 

 

Human Cases (confirmed)

Positive Corvids (confirmed)

Positive Mosquito pools

Positive Equine Cases

BC

2

0

10

2

Alberta

2

n/a

n/a

0

Saskatchewan

1

1

11

0

Manitoba

0

0

2

0

Ontario

0

5

11

1

Total

5

6

34

3

AB, SK and MN and ON are not testing corvids as part of their WNv programs, all birds have been tested by the Canadian Cooperative Wildlife Health Centre

AB is not testing mosquito pools

WNV Activity in the US

  • Washington:
    • There have been 17 human cases, 326 positive pools, 19 positive birds and 64 positive horses.
    • This is the highest number of human cases reported in a season by Washington State.
    • Most activity continues to be reported in the Southern and Central area of the State.  Grays Harbour County, located on the west coast of the State reported their first activity.
    • A recent human case in Whatcom country was associated with travel to Eastern Washington. 
  • Oregon:
    • There have been 7 human cases, 15 positive birds, 5 positive horses and 266 positive mosquito pools reported. 
    • Activity continues to be reported in only 5 Counties located in the north and eastern part of Oregon.
  • California: 
    • There have been 47 human cases reported in 41 counties, 443 dead birds, 967 mosquito pools, 255 sentinel chicken flocks, 9 horses and 9 squirrels have been reported as positive to date in 2009.

 

Other US states reporting WNV activity:

(Data as of Sept 15; Sources:  USGS survey)

280 human cases of WNV have been reported in 30 States.  49% of human cases have been reported as encephalitis/meningitis.  Eight fatalities have been reported.  The number of human cases reported continues to be lower compared to previous seasons.  



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