It is impossible to tell from a mosquito bite on the skin surface whether the mosquito was carrying an infection such as WNv. Research indicates that approximately four out of five people who are bitten by an infected mosquito do not show any symptoms. Of those that show symptoms, most will experience mild illness including fever, headache, body ache, nausea, vomiting and rash on chest, stomach or back. Only about 1 in 150 people infected will experience serious symptoms including high fever, severe headache, muscle weakness, stiff neck, confusion, tremors, numbness and sudden sensitivity to light.

Symptoms usually develop between two and 15 days after being bitten by an infected mosquito.

Your physician has the information available to determine if you need to be tested for WNv.

If you have any of the following symptoms, seek medical help. These may be early symptoms of WNv illness, or of many other illnesses, so seek medical attention to find out the cause.

• fever
• muscle weakness
• stiff neck
• confusion
• severe headache
• sudden sensitivity to light.

Extreme swelling or infection at the site of the mosquito bite is another reason to seek medical attention. This may or may not indicate WNv infection.

Since July 2003, Canadian Blood Services has had a test that screens every blood donation for West Nile virus. Giving blood is safe and it's very much needed. However, if you have donated blood and begin to feel ill after your donation, please contact Canadian Blood Services at 1-888-2-DONATE (1-888-236-6283).

• West Nile virus (WNv) is spread to humans by the bite of an infected mosquito. Mosquitoes become infected when they bite an infected bird.
• The virus is not spread by person-to-person contact through touching, coughing, sneezing, or drinking from the same cup.
• There is some evidence that a person can be infected by handling a dead bird, however, the risk is very low. Wear gloves or use a thick plastic bag if you have to handle a dead bird.
• WNv is not known to be transmitted from mammals, such as horses, to humans.

May 2005

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