• Until 1999, WNV was commonly found in Africa, Eastern Europe, West Asia and the northern Mediterranean area: there have been outbreaks of WNV in Egypt, Israel, India, France, Romania and the Czech Republic.
• In 1999, the first North American cases occurred in New York City. It is not known how the virus was introduced into the New York area. 
• Since then, it has established itself in nearly all of the United States (lower 48 States) and much of Canada (see the West Nile Virus in North America map). It has now been detected in B.C.

How serious is WNV?

• Most infected people will never know they’ve had the disease. Research indicates that only about one out of every five people who are bitten by a mosquito and infected with WNV will develop symptoms.
• Most people who do develop symptoms will experience varying degrees of an illness known as West Nile Non-neurological Syndrome. Even non-neurological forms of the disease may cause lasting health effects, including muscle weakness, memory problems and fatigue which may continue for months. 
• In less than one per cent of infected individuals (about one in 150), WNV can cause severe illness resulting in hospitalization. This includes swelling of the brain (encephalitis), inflammation of the lining of the brain (meningitis) or polio-like paralysis.
• The fatality rate is about 0.1 per cent.

• fever
• headache
• muscle weakness
• muscle and/or joint aches
• malaise
• rash
• sensitivity to light

• severe headache
• stiff neck
• meningitis
• encephalitis
• paralysis

Symptoms begin approximately three to 14 days after being bitten by an infected mosquito. Recovery from symptoms may occur in about a week with West Nile non-neuorolgoical syndrome and may take a year or more for West Nile neurological syndrome.

• People usually become infected with the virus through a mosquito bite.
• WNV is not spread through person-to-person contact such as touching, coughing, sneezing or drinking from a shared cup.
• Although the virus is not known to be transmitted to humans from animals, people should avoid handling dead animals or birds with their bare hands. 
• Less commonly, WNV can be transmitted through blood transfusion and organ transplants if the donor was recently infected with WNV.
• WNV can also be transmitted from a mother to her unborn child or through breast milk, but these events are rare. The benefits of breastfeeding outweigh the risk from WNV.

How likely am I to get sick with WNV from one mosquito bite?

• In areas where mosquitoes do carry the virus, usually only a small number of mosquitoes will be infected.  Most mosquitoes that bite humans are not able to carry WNV, but there is no easy way to tell the difference between ones that can and ones that can’t so it is important to prevent any mosquito bite.
• In BC, we monitor Culex tarsalis and Culex pipiens mosquito species because they are the most likely to transmit WNV between birds, humans, and other animals in our region (they are competent vectors).

Who is at risk for WNV?
Everyone who is outside during the summer months gardening, golfing, walking, camping etc. is at risk once the virus is in the area and should take precautions to avoid mosquito bites. While anyone can be infected with WNv, the chances of having a severe illness are greater as you get older, even if you are healthy. You may also be at greater risk if you have a weakened immune system.

• Clean up areas where mosquitoes like to breed. It doesn’t take much time (generally one week), or water for mosquitoes to develop from eggs into adults.
• Take a look around your home and get rid of mosquito-friendly places that would make good breeding sites or resting places for mosquitoes.
• Remove any type of standing water at least once a week.
• Clean up and empty containers that collect water such as old tires, flower pots, wheelbarrows, barrels, tin cans or even small containers like bottle tops that are outdoors.
• Drill holes in the bottom of used containers so water can’t collect.
• Change water in bird baths at least once a week.
• If you have a swimming pool, immediately remove water that collects on pool covers and make sure the pool’s pump is circulating
• Turn over wading pools when not in use.
• Check leaves and drains: don’t let things pile up.
• Clear leaves and twigs from eaves troughs, storm and roof gutters throughout the summer.
• Check flat roofs frequently for standing water.
• Make sure drains and drainage ditches are not clogged.
• Stop mosquitoes from entering your home
• Check windows and door screens for holes and make sure they fit snugly into the frames, so mosquitoes cannot get in.

• If you can, avoid being out from dusk to dawn as mosquitoes that carry WNV tend to be active at these times.
• Wear protective clothing, especially outside in the early evening and at dawn. This includes long-sleeve shirts or jackets and long pants that mosquitoes cannot bite through. Tuck your pants into socks for extra protection.
• Avoid dark coloured clothing as it can attract mosquitoes.
• Use mosquito netting for babies and toddlers in cribs and strollers.
• Use mosquito repellent. Putting on personal insect repellents that are federally registered, such as those that contain DEET (N,N-Dethyl-m-toluamide) is an effective way to protect yourself from mosquito bites.
• There are also many repellents that have been shown NOT to protect against mosquito bites, including bug zappers, devices that give off sound waves and Citrosa plants.
• Tips when using insect repellent:
• Apply repellent sparingly on exposed skin or on top of clothing. Do not use under clothing.
• The repellent doesn’t have to be applied heavily to work- a light coating will do.
• Use your hands to rub the repellent over your skin after you spray it on. Research shows that mosquitoes will find and bite even very small sections of skin missed by the spray.
• Do not use repellent on open wounds, or if skin is irritated or sunburned.
• Do not get repellent in your eyes – if this happens, rinse with water right away.
• Avoid breathing mist from spray-type repellent. Always apply in a well-ventilated area; never apply spray repellent inside a tent.
• Do not use near food.
• Read the manufacturer’s instructions on the label carefully, including restrictions for use on young children and maximum number of applications per day.

• DEET is the short name for N,N-Dethyl-m-toluamide, a personal insect repellent that is approved for use in Canada.
• Insect repellents work by preventing insects such as mosquitoes from landing on and biting humans; they are not the same as insecticides which kill the insects.
• Never use a product labeled as an ‘insecticide’ on your body.
• The concentration of DEET should be no greater than 30% for adults and 10% for children; check the percent listed on the label to be sure.
• Studies have shown that products with lower concentrations of DEET are just as effective as the high concentration products, but they remain effective for shorter periods of time:
• Choose a product that meets your specific needs. For example if you plan to be outdoors for a short period of time, choose a product with a lower concentration of DEET and repeat only if you need a longer protection time. To see more information on the different types and the time to use the insect repellent, please click here
• More information on DEET and children
• Repellents containing DEET should not be used on children under 6 months of age.
• Use sparingly on children, avoid their face and hands.
• Use the least concentrated product (10% or less) on children 6 month to 2 years and apply only once a day.
• Don’t apply DEET more than three times a day to children 2-12 years of age.
• Always supervise children using insect repellents and avoid getting repellent on children’s hands to reduce the chance of getting the repellent in their eyes and mouths.
• Safety Tips on Using Personal Insect Repellents from Health Canada
• Statement on Personal Protective Measures to Prevent Arthropod Bites from Public Health Agency of Canada

• There are effective insect repellents registered in Canada that contain active ingredients other than DEET. These include repellents with p-Menthane-3,8-diol (PMD), also known as lemon-eucalyptus oil.
• This product has been shown to be as effective as DEET but the duration of protection is only about 3 hours for mosquitoes.
• Lemon eucalyptus oil should not be used on children less than three years old.
• Soybean oil products are also effective mosquito repellents but are not yet widely available in Canada.
• Products with the substance picaridin are also effective but are not yet available in Canada.
• Instructions for proper use are listed on each product label.

• Health Canada, Insect repellent information
• Public Health Agency of Canada, Re-evaluation of Citronella
• BCCDC, Insect repellent poster  [PDF, 400KB].

Other repellents
Novel pest control products such as DEET-alternative personal repellent and environmental barrier repellents periodically appear in the popular media and market. The commercial opportunity of introducing a new product to repel mosquitoes may be compelling. But do these products actually work, and are they safe for you and your family?

The Pest Management Regulatory Agency (PMRA), a branch of Health Canada, is responsible for pesticide regulation in Canada. Pesticides are stringently regulated in Canada to ensure they pose minimal risk to human health and the environment.

 Discussed below are some recently introduced mosquito repellent products available in the market.These products are presented as examples only and are not necessarily endorsed by the BC Centre for Disease Control or Health Canada.

• Personal repellent

Skin patches are being promoted in the popular media for a wide range of conditions, including advertisements for Vitamin B patches claiming to repel mosquitoes.In the United States (US) such a patch would be considered a biochemical pesticide and require registration under their pesticide registration process. Ives et al. (2005) evaluated Vitamin B as a mosquito repellent, and found that differences in the feeding behaviour of Anopheles stephensi were greater between individuals than between treatment groups.There is some limited evidence that Vitamin B might reduce the immune response to the injected fluids of the mosquito salivary gland in other animals but not in humans.Therefore, there is no evidence to support the use of Vitamin B patches as a mosquito repellent. This type of product will not adequately protect you from disease-carrying mosquitoes, so alternative mosquito repelling products with proven effectiveness (e.g. DEET-based repellents) should be used instead.

• Environmental barrier repellents

Smoking coils infused with pyrethrin flowers have been used to reduce mosquito-human contact for over 100 years.The smoke produced by these coils causes confusion among the mosquitoes and impairs its ability to identify humans as a blood-meal, while the pyrethrin knocks-down or kills the insect. Alternatives that produce less smoke have appeared on the market in recent years.The OFF!® PowerPad™ Mosquito Lamp uses a candle, and the ThermaCELL® Mosquito area repellent candle lantern uses butane gas to heat an insecticide-soaked pad to release the chemical into the air. These products claim to be effective in repelling mosquitoes within a 4.5 square metre area, approximately the size of a patio deck.

These modern mosquito coils and mosquito lamps use d-cis-trans allethrin, a synthetic ester that is similar to pyrethrin found in Chrysanthemum flowers.Coils typically use a chemical concentration of 0.3%; whereas, lamps and lanterns use 21.97% concentration of the chemical.Although they may appear less harmful than a mosquito coil because they are smokeless, the mosquito lamps come with health precautions such as “Harmful if inhaled. Avoid breathing vapours. For outdoor use as an insect repellent only.Cover exposed food.”

There are also commercial metered pressurized spray systems that drift pyrethrin pesticide into a free flowing air space such as a barn.These products are often used in commercial facilities requiring an insect-free workspace.Recently however, this technology has been adapted for residential applications.Professional pesticide applicators of the American Mosquito Control Association are not in favour of these devices as outlined in the position on Misting Systems because they promote unnecessary insecticide use.

Registration of products that claim insecticidal properties is expensive. However, not all product registration requires costly pesticide residue tolerance studies. Many organic based oils are exempt from pesticide product registration in the US according to their Federal Insecticide, Fungicide, & Rodenticide Act (FIFRA), including Citronella, Garlic, Mint and Soybean Oil. Different guidelines must be met in Canada before these products can be sold as “Pest Control Products (PCP).” The PMRA PCP number can be used to determine if these products are allowed to be sold a pesticide.

In 2010, the PMRA reviewed the registration of Garlic Oil as a potential outdoor, environmental barrier repellent for mosquitoes.A product named Comfort Zone was approved according to Registration Decision 2010-16.Many people are looking for a natural and easy way to repel mosquitoes and this outdoor barrier spray for grass and shrubs may be an alternative. The effectiveness of this product has not been critically evaluated so using a repellent on exposed skin, such as DEET or Lemon Eucalyptus Oil to protect yourself from disease carrying mosquitoes, is also recommended.

If I am breast-feeding, can I use an insect repellent containing DEET?  

• Yes, there are no reported problems with pregnant or breast-feeding women using repellents with DEET.
• Use sparingly in the lowest concentration you need.