Manitoba Health: West Nile virus

June 13, 2013

Manitoba Health reports that mosquito surveillance activities have commenced in the province for the 2013 season.

At this time the risk of exposure to WNV is low.

In southern Manitoba, anyone can be exposed to an infected Culex tarsalis mosquito during the summer months. Severe illness has occurred in all age groups. Severe illness has occurred more often among older adults or people with chronic health conditions or weakened immune systems.

In Manitoba, West Nile virus (WNV) is transmitted to humans primarily by the Culex tarsalis mosquito, usually during late June, July, August and early September. This risk varies from year to year based on precipitation, temperature, mosquito population and other factors.

WNV can cause severe illness (West Nile virus neurological syndrome) including encephalitis, an inflammation of the brain. The severe illness can be life-threatening and may result in long-term disability. Since 2003, the annual number of severe cases of WNV in Manitoba has ranged from one to 72; WNV-related deaths have ranged from none to four per year.

More people develop a milder illness (West Nile virus Non-neurological Syndrome) with symptoms such as fever, headache, fatigue, body aches and rash.

Most people infected with WNV have no symptoms and do not become ill.

There is no vaccine or specific treatment for WNV. Milder symptoms of WNV Non-neurological Syndrome usually resolve without medical care. Anyone experiencing severe symptoms (ex: persistent high fever, muscle weakness, headache) should seek medical attention promptly for diagnosis and care.

How do I protect against West Nile virus?

Reduce the time you spend outside between dusk and dawn.
Apply an appropriate mosquito repellent.
Wear light-coloured, loose-fitting clothing with long sleeves and pant legs.
Make sure your door and window screens fit tightly and are free of holes..

Regularly clean and empty eaves troughs, pool covers and other items that might collect water.
Clean and empty bird baths weekly
Make sure openings in rain barrels are covered with mosquito screening or tightly sealed around the downspout.
Clear your yard of old tires or other debris where water collects.
Cut the grass around your home; trim hedges and trees around doorways and seating areas.