How the virus is spread
West Nile Virus (WNV) is spread to humans by the bite of an infected mosquito. Mosquitoes become infected by biting an infected bird. The virus is not spread by person-to-person contact. It cannot be spread directly from a bird to a human. On very rare occasions WNV has been spread through blood transfusions, organ transplants, and from mother to child during pregnancy, birth, breastfeeding or chestfeeding.
Symptoms
No symptoms, most people
The risk of becoming seriously ill from WNV is low. Most people (about 4 in 5) infected with WNV will not have any symptoms.
Febrile Illness (fever), approximately 20% of people
About 1 in 5 people infected with WNV will become sick with fever, and other symptoms such as headache, body aches, vomiting, diarrhea, tiredness, or rash. Symptoms usually last from a few days to a few weeks, and most people recover completely. Symptoms of WNV usually appear within 2 to 14 days after being bitten.
Severe illness, small number of cases
About 1 in 150 people infected with WNV will develop serious symptoms affecting their nervous system such as encephalitis (swelling of the brain) or meningitis (swelling of the membranes surrounding the brain and spinal cord)
Severe illness is most likely to occur in older people and in people who have poorly functioning immune systems due to other medical conditions or certain medications. About 1 in 10 people who develop severe illness with WNV die from it. If you have any of the following symptoms after being bitten by a mosquito, get medical attention immediately:
- Rapid onset of severe headache.
- High fever.
- Stiff neck.
- Loss of consciousness.
- Confusion or drowsiness.
- Tremors or convulsions
- Numbness or paralysis.
- Muscle weakness
- Loss of vision
Extreme swelling or infection at the site of the mosquito bite is another reason to get medical attention.
Protect yourself and your family from mosquito bites:
- Apply a Health Canada approved insect repellent containing DEET or Icaridin to exposed skin and clothing. Visit the Canadian Paediatric Society for information on insect repellent use for young children.
- Wear light coloured long-sleeved shirts, closed toe shoes, long pants and a hat, especially at dawn and dusk. Mosquitoes are attracted to dark colours.
- Stay out of wooded areas during dawn and dusk.
- Make sure that screens for doors and windows have no holes and fit tightly.
- use fine mesh netting on playpens or strollers when you are in an area with mosquitoes
- Clean up standing water in you yard
Make sure mosquitoes are unable to breed on your property:
Mosquitoes can lay their eggs even in small amounts of standing water. It takes about four days for the eggs to grow into adults. Health Canada recommends:
- draining standing water two times a week from items like pool covers, saucers under flower pots, recycle bins, and garbage cans,
- removing unused items (i.e., old tires) from around your property that may collect water,
- drilling holes in tire swings so water can drain out,
- changing the water in children's wading pools, bird baths, pet bowls and livestock watering tanks twice a week,
- covering rain barrels with screens, and
- cleaning out eavestroughs regularly to prevent clogs that can trap water.
If you find a dead bird on property:
- Avoid touching dead birds with bare hands where possible, instead, use a tool like a shovel to dispose of it. If you must handle the bird, wear rubber gloves and wash hands well with soap and water after handling.
- In most cases, dead animals can be put in the garbage or buried. If you are uncertain about disposal requirements, please consult your local municipality.
- Report dead birds to the Canadian Wildlife Health Cooperative.