Updated: October 2001
Infectious diseases not necessarily common in Canada can occur and may even be widespread in other countries. Standards of hygiene and medical care may differ from those at home. Before departure, you should learn about the health conditions in the country or countries you plan to visit, your own risk of disease and the steps you can take to prevent illness.
The risk is yours
Your risk of acquiring
a disease depends on several factors. They include: your age,
gender, immunization status and current state of health; your
itinerary, duration and style of travel (e.g., first class,
adventure) and anticipated travel activities (e.g., animal contact,
exposure to fresh water, sexual contact); as well as the local
disease situation.
Risk assessment consultation
The Public
Health Agency of Canada strongly recommends that your travel plans
include contacting a travel medicine clinic or physician 6 to 8
weeks before departure. Based on your individual risk assessment, a
health care professional can determine your need for immunizations
and/or preventive medication (prophylaxis) and advise you on
precautions to avoid disease.
Some facts from the experts
The information below has been developed and is updated in
consultation with Public Health Agency of Canada's Committee to Advise on Tropical
Medicine and Travel (CATMAT). The recommendations are intended
as general advice about the prevention of measles for Canadians
travelling internationally.
Disease profile |
West Nile (WN) virus is a mosquito-borne flavivirus that can cause flu-like symptoms in infected individuals. In rare cases, it can lead to meningitis (inflammation of the lining of the brain and spinal cord) or encephalitis (inflammation of the brain). WN virus was first isolated in 1937 in the West Nile province of Uganda.
West Nile virus is spread to humans by the bite of an infected mosquito. A mosquito becomes infected by feeding on the blood of a bird that carries the virus. There is no evidence to suggest that WN virus can be transmitted from person to person.
Many mosquito species can become infected with WN virus. Culex pipiens, Culex restuans and Culex salinarius mosquitoes, which are dusk-to-dawn biters, and Aedes japonicus and Aedes triseriatus mosquitoes, which are daytime biters, have been shown to be infected. However, Culex pipiens and restuans appear to have been the species most commonly infected during the outbreaks in the eastern United States in 1999 and 2000.
The number of bird species in North America that can carry WN virus is not known at this stage, although approximately 76 species were affected during the 1999 and 2000 outbreaks in the eastern USA. The group that appeared to be most affected was corvids, such as crows, ravens and blue jays.
In the eastern United States, there have been cases of WN virus documented in other animals: cat, domestic rabbit, chipmunk, gray squirrel, striped skunk, bats and horses. For animals which show symptoms, these could include any combination of the following: fever, weakness, lack of coordination, muscle spasms, seizures and/or changes in temperament or personality. There have been no documented cases of one animal infecting another animal, or of an animal infecting a human.
Geographic distribution |
Outbreaks of WN virus have occurred in several countries including Egypt, Israel, South Africa, and parts of Asia and Europe. Recent outbreaks, outside of North America, have occurred in France and Israel in 2000, Russia in 1999 and Romania in 1996-97.
The first outbreak of WN virus in North America occurred in and around New York City late in the summer of 1999. There were 62 confirmed cases (mostly elderly people), with seven deaths, including one Canadian who had visited New York City during the time of the outbreak. In the summer of 2000, there were 21 confirmed cases in New York City and the states of New Jersey and Connecticut, resulting in two deaths. There was considerable WN virus activity in Massachusetts, Rhode Island, New Hampshire, Maryland, Pennsylvania, Vermont, Virginia, North Carolina and the District of Columbia (Washington). The virus had been detected in dead birds, mosquitoes, horses and other animals in a number of counties in these states.
Symptoms |
Symptoms can begin 3 to 15 days following the bite of an infected mosquito. However, most people who are infected with WN virus show no symptoms at all or may experience only mild flu-like symptoms such as fever, headache and body aches before fully recovering. Reports from countries outside of North America indicate that some persons may also develop a mild rash or swollen lymph glands.
In rare cases, particularly among the elderly, very young, and those with suppressed immune systems, infection with WN virus can result in serious illness such as meningitis (inflammation of the lining of the brain and spinal cord) or encephalitis (inflammation of the brain). Symptoms for these conditions could include rapid onset of severe headache, high fever, stiff neck, vomiting, drowsiness, confusion, muscle weakness, and loss of consciousness (coma). People who have a sudden onset of these symptoms should seek medical care immediately. In some people with serious illness death may occur.
Treatment |
Prevention and personal precautions |
Personal measures to avoid mosquitoes
Public Health Agency of Canada encourages travellers to areas with West Nile virus activity in mosquitoes, birds and particularly in humans, to take personal insect precautions at all times while outside to avoid being bitten.To reduce your exposure to mosquitoes, consider the following measures:
- remain in well-screened or completely enclosed, air-conditioned areas;
- wear light-colored clothing with full-length pant legs and sleeves; and
- use insect repellent on exposed skin.
The use of insect repellent on exposed skin is strongly recommended. Of the insect repellents registered in Canada, those containing ‘N, N diethyl-m-toluamide' (DEET) are the most effective. Although the concentration of DEET varies from product to product, repellency rates are largely equivalent. In general, higher concentrations protect for longer periods of time, but there is little advantage in the duration of repellence with DEET concentrations > 30%, and there may be additional risk of toxicity with higher concentrations. New microencapsulated products containing 33% DEET are registered in Canada, and they should provide 8 hours of protection.
Children and DEET
In rare instances, application of insect repellents with DEET has been associated with seizures in young children (14 cases have been reported in over 30 years of DEET use and billions of applications every year). The actual concentration of DEET varies among repellents and can be as high as 95%. However, repellents with DEET concentrations of 10% are very effective and should last three to four hours. For children, DEET in a concentration of not more than 10% should be applied sparingly to exposed surfaces only and washed off after children come indoors.The likelihood of adverse reactions can be minimized by the following precautions:
- Apply repellent sparingly and only to exposed skin.
- Avoid applying high concentration products.
- Avoid applying repellents to portions of children's hands that are likely to contact the eyes or mouth.
- Never use repellents on wounds or irritated skin.
- Wash repellent-treated skin after children come indoors. If a reaction to insect repellent is suspected, wash treated skin and seek medical attention.
Labels on DEET-containing products in Canada currently indicate that the use of DEET on children under 2 years of age is not recommended. However, as a result of Public Health Agency of Canada's Pest Management Regulatory Agency's (PMRA) re-evaluation of DEET and consultation with the Canadian Pediatric Society, PMRA now recommends the following for children under 2:
on children under 6 months of age:
that insect repellents containing DEET still not be used;on children aged 6 months to 2 years:
that the use of 1 application per day may be considered in situations where a high risk of complications from insect bites exists. The product should be applied sparingly and not be applied to the face and hands; only the least concentrated product (10% DEET or less) should be used, and prolonged use should be avoided;on children between 2 and 12 years of age:
that the least concentrated product (10% DEET or less) be used and that it be applied no more than 3 times per day.Sources: Centre for Infectious Disease Prevention & Control and the National Microbiology Laboratory of the Public Health Agency of Canada.
For more information on repellents and DEET use, go to: Safety Tips on Using Personal Insect Repellent
.
Some things to think about... |
Most people who are infected with WN virus show no symptoms at all or may experience only mild flu-like symptoms such as fever, headache and body aches before fully recovering.
For more information...