August 13, 2008
Media Release

York Region reports first cases of West Nile virus (WNV) activity
Lab results confirm one mosquito pool and one human case have tested positive for WNV

NEWMARKET – The Regional Municipality of York Community and Health Services Department reports
one mosquito pool and one human case have tested positive for West Nile virus (WNV) in York Region. 
The mosquitoes that tested positive for WNV came from a “pool” in the Town of Markham, close to the intersection of Leslie Street and Steeles Avenue.  A “pool” defines one batch of mosquitoes caught overnight in one trap and sent for testing.
The infected individual, a 28-year-old female from the Town of Markham, is recovering from a mild form of the disease.  The exact location of the incident is still under investigation, but the exposure site is believed to be in the Major Mackenzie Drive and Highway 48 area.
This is the first human case of WNV in Ontario in 2008.  In 2007, there were 17 human cases reported in Ontario.
“On-going treatment of the catch basins in both of these areas will continue, as well as the necessary treatment of surrounding stagnant water on public property,” said Dr. Karim Kurji, York Region’s Medical Officer of Health and Director of Public Health Programs.  “Surveillance for the virus will also be increased in the affected area.”
Trapping mosquitoes, bird and human surveillance are part of the 2008 York Region WNV control plan. 
Like in humans, WNV is transmitted to the bird population by infected mosquitoes.  Crows, blue jays and other raptor species are known to be most susceptible to the disease and act as early warning signs for the presence of the virus in a particular area.
Report dead crows and blue jays:  York Region Community and Health Services requests that residents report sightings of dead crows and blue jays through the Health Connection information line.  Suitable specimens may be collected and submitted to the Canadian Co-operative Wildlife Health Centre in Guelph for testing.  All crows and blue jays that are reported will help to map out possible WNV activity in York Region.
Dead bird pickup service is available:  Most dead birds will not be suitable for testing, but knowing what species they are and where they died is important information.  Do not handle birds with bare hands or dispose of dead birds through the municipal garbage systems.  Please contact Health Connection for pickup of dead birds of any species.
WNV illness can range from mild symptoms including rash, joint pain and fever to more severe symptoms including confusion, severe headache and a sudden sensitivity to light.  In rare cases, neurological illness including encephalitis (inflammation of the brain) can also occur.  Symptoms of WNV typically appear three to 15 days after being bitten by an infected mosquito.  Those experiencing symptoms should seek
medical advice.
Prevention and protection are the best ways to protect yourself and your family from WNV.  There are simple and common sense precautions that should be taken:
• Minimize outdoor activities where and when mosquitoes are most active such as dusk, night and dawn
• Wear protective clothing such as long-sleeved shirts, full-length trousers, socks, light-coloured clothing and tuck pant legs into socks when possible
• Consider using an insect repellent as directed
• Make sure screens on your home are tight-fitting and in good repair
• Eliminate stagnant water around your property which may gather in pool covers, flower pots, children’s pools, old tires and birdbaths
The York Region WNV control plan for 2008 includes:
• Mosquito, bird and human surveillance
• WNV control activities, including a larviciding strategy:
• Four applications (June, July, August and September) of larvicide target all catch basins along regional and municipal roads and in catch basins, as required, on private property
• Larvicide interferes with the mosquito life cycle, preventing the mosquito larva from reaching maturity
• Larvicide has been approved by both the provincial and federal governments and is considered low risk for humans, pets and the environment
• Larvicide is applied by Ministry of the Environment licensed applicator Canadian Centre for Mosquito Management Inc. 
• Catch basins which have been treated will be marked with a coloured dot
• Residents concerned about catch basins on private property are requested to place a mesh screen over the basin to prevent mosquitoes from entering and exiting
• A limited number of rear-yard catch basins located on private property will be treated with larvicide on a case-by-case basis
• In addition, larvicide may be placed in ditches and temporary or permanent standing water pools, including storm water management ponds, if evidence of mosquito breeding is found 
To report a dead crow or blue jay or for more information on WNV or any other health-related topic, please contact York Region Health Connection at 1-800-361-5653.
To review the current status of WNV in Ontario, visit
For more information on The Regional Municipality of York, please visit

Jennifer Mitchell-Emmerson, Community and Health Services, York Region

                                 Phone:  905 830-4444, ext. 4016 or After-hours Cell:  905 221-5553


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