Mosquito

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  • West Nile Story - One Year Later (PDF) From DUC's Conservator magazine, Dr. Dale Wrubleski updates us on the story of West Nile virus (2004).
  • West Nile Story
    From DUC's Conservator magazine, Dr. Dale Wrubleski uses his entomology expertise to provide us with a valuable insight into West Nile virus (2003).
 

Human Infection Estimates

It has been estimated that in areas where West Nile virus is present, less than one per cent of mosquitoes are infected with the virus. If we consider 2,000 people who are bitten by West Nile virus infected mosquitoes:

  • Approximately 1,600 of these 2,000 people will experience no symptoms.
  • Approximately 400 of these 2,000 people will become ill.
  • Approximately 387 of these 400 people will develop a mild illness with flu-like symptoms including nausea, vomiting, headache, muscle pains and rash.
  • Approximately 13 of these 400 people will develop serious symptoms and require hospitalization. Symptoms of West Nile encephalitis or meningitis include severe headache, high fever, paralysis, muscle weakness and convulsions.
  • Of the 13 people who are hospitalized, it is thought that one person may die, while the other 12 will recover with possible long-term neurological impairment. The interval between infection and the onset of disease in people is usually between three and 14 days. Serious disease is more common in people over age 50.

Very rare and unexpected transfer of virus in North America.

  • transfusions
  • organ transplants
  • breastfeeding
  • intrauterine – from mother to fetus during pregnancy
  • occupational exposure — handling infected birds

West Nile Virus Cases in Canada

(data from Health Canada as of June 26, 2009)
  horse cases human cases1 human deaths number of provinces where detected2
1999 0 0 0 0
2000 0 0 0 0
2001 0 0 0 1 (ON)
2002 356 414 18 5 (NS, QC, ON, MB, SK)
2003 445 1495 10 9 (NB, NS, QC, ON, MB, SK, AB, BC3, YK3)
2004 14 26 0 5 (QC, ON, MB, SK, AB)
2005 n/a 238 n/a 8 (PEI3, NS3, NB3, QC, ON, MB, SK, AB)
2006 13 154 2 5 (QC, ON, MB, SK, AB)
2007 109 2,401 12 7 (NS3, QC3, ON, MB, SK, AB, BC3)
2008 6 38 0 6 (QC, ON, MB, SK, AB3, BC3)

1includes confirmed and probable cases
2includes virus detected in mosquitoes, birds, horses and/or humans
3related to travel outside the province/territory

West Nile Virus Cases in United States

(data from Centers for Disease Control and Prevention, USDA Animal and Plant Health Inspection Services as of April 10, 2009)
  horse cases human cases human deaths number of states where detected
1999 25 62 74 4
2000 60 21 2 12
2001 738 66 9 27
2002 15,257 4,156 284 44
2003 5,181 9,862 264 46
2004 1,406 2,539 100 47
2005 1,088 3,000 119 48
2006 1,086 4,269 177 44
2007 468 3,598 121 43
2008 178 1,356 44 47

4 includes one Canadian who visited New York during the outbreak

<< Page 3: How It's Transmitted
Page 5: Prevention & Control >>

 
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