Every summer mosquitoes arrive with the warmer weather and Albertans are reminded, particularly seniors, to take precautions to reduce their risk of acquiring West Nile virus (WNv).
People spending time outdoors, particularly those over age 50, need to take precautions. Some people think being bitten by mosquitoes will increase their immunity to WNv, but it remains uncertain whether or not humans develop long-lasting immunity after being bitten by an infected mosquito.
Most people who become infected with WNv have no symptoms. Of the 20 per cent who become ill, WNv symptoms will usually appear within three to 14 days.  Symptoms vary but can include fever, severe headache, chills, rash and body aches. Less than one percent of those infected will develop the more severe form of the disease, West Nile Neurological Syndrome.
Individuals who develop West Nile Neurological Syndrome are usually severely ill and can develop long lasting side effects. In some cases it can be fatal. A total of 320 human cases of WNv were reported in Alberta in 2007. Of that number, 21 cases were classified as West Nile Neurological Syndrome. These numbers are higher than the previous year.
If you plan to be outside to plant shrubs, water the lawn, play baseball or just sun in the back yard, apply a repellant containing DEET according to package instructions. At dusk and dawn, wear long-sleeved tops and pants.
See video How To Protect Yourself From West Nile Virus.
As for predicting how prevalent WNv will be this summer, it will depend on how warm the weather becomes. Culex tarsalis mosquito numbers usually peak in late July and throughout August, making this the most likely time for the WNv to spread to both animals and humans.