WEST NILE VIRUS

Summer Season Means Mosquito Season

Mosquitoes. They’ve always been a summer-time nuisance, especially for anyone who likes to spend time outdoors. But since the appearance of the West Nile virus here in Ontario , they’ve become a little more than just pesky.

Only a few species of mosquitoes found here in Ontario carry West Nile virus. The most common is Culex pipiens (nicknamed the rain barrel mosquito), which lives near humans, much like the common housefly. Scientific research indicates that four out of five people bitten by a mosquito infected with West Nile virus do not show any symptoms of the illness. The risk of being bitten by an infected mosquito depends on how many virus-carrying mosquitoes are present in a specific area.

The Ministry of Health and Long Term Care is the government lead on West Nile virus protection and control in Ontario . Regional and municipal health authorities decide what mosquito control measures will be carried out locally, by monitoring the status of the virus – including in provincial parks. Ontario Parks supports regional health units in their efforts to educate people how they can fight the bite. Health authorities will decide, in consultation with Natural Resources and Environment ministry officials, whether there is a need to spray to control mosquitoes in campgrounds, wetlands and other sensitive natural areas within provincial parks this summer.

Spraying to curb the spread of West Nile virus has environmental, health and practical concerns. Preventing mosquito bites before they happen is still the best weapon in our effort to control the spread of the West Nile virus in people.

The West Nile virus is a mosquito-borne virus that can cause mild symptoms or occasionally a more serious illness. Although the chances of a person getting sick are small, there are some simple steps you can take to reduce your risk of being bitten by mosquitoes, such as covering up and using an insect repellent.

How do people become infected with West Nile virus?
People become infected with West Nile virus primarily through the bite of a mosquito that carries the virus. Mosquitoes become infected with West Nile virus when they feed on the blood of infected birds. These infected mosquitoes can then transmit West Nile virus to humans and to other birds. West Nile virus is not known to be spread by birds or other animals to people or by direct person-to-person contact.

What is the risk for becoming ill?
Everyone who is active and outside during the summer months is at risk from West Nile virus and should take precautions to avoid mosquito bites.

Of the dozens of species of mosquitoes found here in Ontario , only a small percentage carry the West Nile virus. The most common is Culex pipiens (nicknamed the rain barrel mosquito), which lives near humans, much like the common housefly. Scientific research indicates that four out of five people bitten by a mosquito infected with West Nile virus do not show any symptoms of the illness.

The risk of being bitten by an infected mosquito depends on how many of the small number of mosquito species that actually carry the virus are present in a specific area.

What effect does West Nile virus have on people?
Only a small percentage of bites from an infected mosquito may lead to West Nile virus infection and, in turn, mild or serious illness.

Most people who become infected will experience no symptoms or have very mild illness. For some, the symptoms will be more pronounced including high fever with muscle weakness, stiff neck, confusion and a severe headache. For a very rare few, the virus causes serious neurological illness. Symptoms generally occur from 5 to 15 days after exposure. For more information, consult your physician.

Can you get West Nile virus from other insects, such as ticks?
At present, scientific research indicates that West Nile virus is only spread to humans through a bite from an infected mosquito.

Tips on Mosquito Behavior

Where do mosquitoes live and breed?
Mosquitoes lay their eggs in moist areas, such as standing water. Many mosquitoes breed in containers that hold water, such as flower pots or discarded tires. The eggs become larva that remain in the water until the adults mature and fly off. Weeds, tall grass and shrubbery provide an outdoor home for adult mosquitoes. They can also enter houses, tents, trailers and RVs through unscreened windows or doors, or broken screens.

Is there a specific time of day when mosquitoes are most active?
Mosquitoes are most active in Ontario from April to October. The season may start later and end earlier in northern Ontario , depending on temperatures. Mosquitoes tend to be most active (and tend to bite more) between dusk and dawn, but they may be present at any time of the day.

Do all mosquitoes bite humans?
Only the adult females of certain mosquito species bite humans. Male mosquitoes feed on nectar and plant juices only. Female mosquitoes feed on humans, birds and other animals to get sufficient blood to develop eggs.