West Nile virus (WNV) is a potentially serious illness that is transmitted to humans through the bite of an infected mosquito. Although the risk of becoming infected with WNV in Toronto is low, protecting yourself against mosquito bites can help reduce the risk even further.  While anyone can be infected with WNV, the chances of having a severe illness are greater as you get older or if you have a weakened immune system.  Children are not at greater risk of illness from WNV.