Probable human case of West Nile virus in York

York region Health Services have announced that preliminary tests indicate that the first probable human case of West Nile virus (WNv) in York has been identified.

The individual, a 47 yearold woman from Markham, did not need to be hospitalized and is recovering at home. Confirmatory tests will be conducted at Health Canada's National Microbiology Laboratory in Winnipeg, with results expected in about a week.

To date, there have been 10 human cases of West Nile virus in Ontario. York has reported 10 positive birds and eight positive mosquito pools so far this season. In 2005, there were five human cases reported in the region.

"The West Nile virus season is still upon us and we must continue to be vigilant in protecting ourselves against it," said Dr. Karim Kurji, acting medical officer of health and director of public health programs for the Region. "There is a misconception that because we are starting to experience cooler temperatures, there is less impact of West Nile virus in our community. In fact, mosquitoes are still active until the first heavy frost."

West Nile virus is a viral disease that can be spread to the human population by mosquitoes, which contract the disease after biting an infected bird. WNv can cause illness in humans, especially the elderly and those with compromised immune systems.

In most WNv cases, people will not exhibit any symptoms. Others may experience mild flu-like symptoms or a rash. In more severe cases (less than one per cent) encephalitis or inflammation of the brain can occur, causing severe muscle weakness, headache, stiff neck, vomiting, nausea and eventual deterioration of consciousness or mental state.

Prevention and protection are the best ways for people to avoid 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.  Mosquitoes breed in still water. 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 2006 includes mosquito, bird and human surveillance, as well as WNv control activities, including a larviciding strategy.

The strategy includes four larvicide applications, which have all been completed. These applications targeted all catch basins along Regional and municipal roads and in catch basins, as required, on private property

Methoprene is the larvicide that was used. It comes in a slow-release pellet-like formulation and was administered in catch basins when the mosquito is in the larval stage of development. It was meant to interfere with the mosquito life cycle, preventing the mosquito larva from reaching maturity. It was not sprayed. It has been approved by both the provincial and federal governments and is considered low risk for humans, pets and the environment when it is applied according to label directions

The WNv control plan also includes public education regarding common sense and effective measures to prevent exposure to WNv.

To report a dead crow or blue jay and for more information on WNv or any health-related concern, contact York Region Health Services Health Connection at 1-800-361-5653 or visit www.york.ca