West Nile Virus Surveillance Summary #11

Feb. 10, 2010, 10:33 a.m.

 

Thursday, October 8, 2009

WNV Activity in BC

(Data as of October 7, 2009)  

A probable human WNV infection has been reported in a resident of Interior Health.  The case reported non-neurological symptoms and is linked to travel to Saskatchewan.  One additional horse infection was also reported from the S. Okanagan for a total of three equine infections in 2009. 

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

371

144

394

2474

-

# Positive

3** (1)

0

 

10

3

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

** one case is classified as probable, confirmatory testing is pending.

The number of cases in brackets denotes the number of cases considered to be travel-related.   

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

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 26, 2009)  

Ontario and Manitoba each reported their first human infections.  Overall, two human infections were reported as neurological syndrome (25%).  Activity in Canada was lower than compared to previous seasons, although BC saw their highest WNV activity to date.  

 

Human Cases

Positive Corvids (confirmed)

Positive Mosquito pools

Positive Equine Cases

BC

3

0

10

3

Alberta

2

n/a

n/a

0

Saskatchewan

1

1

11

0

Manitoba

1

0

2

0

Ontario

1

6

14

1

Total

8

7

37

4

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 27 human cases, 341 positive pools, 20 positive birds and 67 positive horses.
    • This is the highest activity in a season reported for human and equine cases and mosquito pools.
    • Most activity was reported in the southern and central parts of the State. 
  • Oregon:
    • There have been 7 human cases, 15 positive birds, 5 positive horses and 266 positive mosquito pools reported. 
    • Activity was reported in 5 Counties located in the north and eastern part of Oregon.
    • The number of human cases reported was lower in 2009 compared to 2008, although the number of positive mosquito pools, birds and horses was higher than the previous season.
  • California: 
    • Activity was reported in 41 counties. There have been 72 human cases, 471 dead birds, 1034 mosquito pools, 330 sentinel chicken flocks, 15 horses and 9 squirrels reported as positive in 2009.
    • Surveillance indicators were lower this season compared to previous seasons in California. 
    • Sixteen counties report human cases, the majority of which were in the southern and central part of the State.
  • Montana:
    • There were a total of 5 human cases, 14 horses and 6 mosquito pools reported positive in 2009.
    • Activity was reported in 6 Counties.  One positive horse was reported in Flathead County which borders with BC.
  • Idaho:
    • 29 human cases were reported in 2009, all were reported in Counties in the southern part of the state.
    • 1 bird and 10 horse infections as well as nine counties reported positive mosquito pools, all were reported also in southern Counties.

 

Other US states reporting WNV activity:

(Data as of Oct 6; Sources:  USGS survey)

436 human cases of WNV have been reported in 33 States.  53% of human cases have been reported as encephalitis/meningitis.  Sixteen fatalities were reported.  The number of human cases reported was lower compared to previous seasons.  

 

 

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