West Nile virus (WNV)

West Nile virus (WNV) belongs to a family of viruses called Flaviviridae. It is transmitted by mosquito bite, and mosquitoes are everywhere, even in the city. Most infected people don’t even realize they are carrying the virus because they have no symptoms. Yet there may be serious consequences for some people.

WNV in Québec

The WNV has been in Québec since 2002. The virus was first identified over 60 years ago in Central Africa. The virus was later detected in several other parts of the world, specifically in the Middle East, Asia and Europe.

The number of WNV cases in Québec dropped from 2006 to 2010, with no declared cases in 2010. Since August 2011, there have been several cases of WNV infection in southwestern Québec. Heavy rains in the spring and hot summer temperatures resulted in higher mosquito populations.

Surveillance of human cases.

Since 2006, there are no more collections of dead birds to determine whether they are carriers of WNV and to evaluate the presence of the virus in the Québec regions.

Transmission of the virus

The main mode of transmission for WNV is through mosquito bites. Mosquitoes become virus carriers after biting infected birds. Since mosquitoes can bite more than once, they can then transmit the virus by biting another animal or a person. While WNV can be transmitted by blood transfusion or organ transplantation, the risk is low. There is no evidence to suggest that the virus can be transmitted from an infected bird or animal to a person.

Symptoms

Most infected people have no symptoms. One infected person in 5 will present mild symptoms such as headaches and fever, sometimes accompanied by body aches, pimples or red spots on the skin. Symptoms take from 3 to 15 days to appear.

Only 1 infected person in 150, which is less than 1%, will develop a serious disease such as encephalitis, which is an inflammation of the brain, or neurological problems that in some cases are permanent.

Health risks generated by WNV vary with age. Complications are very unlikely among children, but more common for those over 50 and for those whose immune systems are compromised by another illness.

When to consult?

People with unusually severe headaches, high fever, a stiff neck, mental confusion or muscular weakness should seek immediate medical attention.

Treatment

At the moment, there is no treatment, remedy or vaccine effective against WNV, but palliative care can stabilize or improve the symptoms of those who are hospitalized.

While WNV infection can be fatal, deaths rarely occur.

Ways to reduce transmission of the virus

Ways to protect yourself from mosquito bites

The normal ways of avoiding mosquito bites are effective against WNV. Even in the city, it is advisable to take the following precautions:

Install screens in good condition on doors and windows, tents and camping shelters.
Wear light-coloured long sleeves and pants during evening outdoor activities.
Avoid exposure to mosquitoes during their peak periods of activity, namely at sunrise and sunset.
Use insect repellents during outdoor activities.

We recommend sensible use of mosquito repellent containing DEET or lemon eucalyptus; these should be used only for prevention of mosquito bites when you are outdoors. Citronella oil-based products are also available; however, they provide protection only for a short time and should be used only for short outdoor activities. You should always read product labels in order to use the product safely. Citronella-based products can repel mosquitoes, but they provide only very short-term protection. As a result, insect repellents containing citronella are not recommended.

Mosquito repellents should be applied in small quantities, only on areas of the body not covered by clothing. It is not necessary to protect children from WNV with insect repellent, since they are not at risk of developing serious illness as a result of infection.

As it is advisable not to put any on the face, especially in young children, repellent can be lightly applied to a hat or cap to repel mosquitoes from the head and face.

If you considering using of insect repellent this summer, consult the repellent chart for some useful tips.

Ways to reduce the number of mosquitoes

The main way to reduce the number of mosquitoes is to Remove stagnant water and clean up your environment.

Mosquitoes breed in water, but it must be stagnant, not running. It is easy to reduce the mosquito population by:

removing or turning over old tires, pails, barrels or any other outdoor object that may collect water;
cleaning the pool and eliminating water accumulating on its cover. If the pool is in use, the flow of water created by the filter keeps mosquitoes away;
keeping garbage cans covered;
fitting rain barrels with mosquito netting;
putting fish that eat mosquito larvae in decorative ponds. In any case should those fish be found in natural watercourses because it could result in a breakdown of the ecosystem.

Using insecticides: It is not recommended to use insecticides on private property without having the expertise to do so. Do not forget that insecticides can be toxic. They generally should only be used by professionals and only after the situation has been assessed by experts.

WNV in the rest of Canada and in the United States

WNV can be contracted in other Canadian provinces and the United States. As of October 23, 2010, 5 people have been infected in Canadian provinces other than Québec.

The Public Health Agency of Canada regularly updates WNV surveillance data for all of Canada. WNV surveillance information about humans and dead birds is available on the Agency’s Web site.

WNV surveillance information for the United States is available on the Centers for Disease Control and Prevention (CDC) Web site

For more information

Consult Institut national de santé publique du Québec documentation on WNV (in French only).
Call Info-Santé at 8-1-1.