What Ontario citizens should do is to clean their gardens and thus prevent the breeding of the mosquitoes. The clear gardens and less plants will reduce the chances of West Nile virus because it is going to reduce the amount of mosquitoes in the area. The authorities ask the people to take advantage of the upcoming weekend and the Victoria Day when most of them are going out to clean their yards.
Removing any standing water from the gardens is also helpful and together with the cleaning, this is going to ruin the love life of the mosquitoes and will reduce their population. The insects use overgrowing bushes as their home and removing the debris will prevent them from settling.
Some other precautions you can take is to check the windows of your house whether there are any holes. Go outside fully clothes and use special sprays against mosquitoes. If you have been bitten by one of those insects and you suspect you may have West Nile virus, seek for immediate medical help.