Source: Health Canada

Know before you go!
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
Health 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. We can help you locate a travel medicine clinic closest to your home.

Some facts from the experts
The information below has been developed and is updated in consultation with Health Canada's Committee to Advise on Tropical Medicine and Travel (CATMAT). The recommendations are intended as general advice about dengue fever prevention for Canadians travelling internationally.

Disease profile
Dengue fever (DF) is an acute viral illness of varying severity. It is caused by one of the four strains, or serotypes, of dengue flaviviruses. The severe form of the virus, dengue haemorrhagic fever (DHF), can be fatal.

Transmission
Dengue fever is spread by the bite of an infected mosquito. Aedes aegpyti, the most common mosquito species that transmits the dengue virus, is a day-time biter and lives in close proximity to humans in urban areas.

Geographic distribution and incidence trends
Dengue fever occurs throughout the tropical and sub-tropical areas of the world, predominantly in urban and surrounding areas, and has been reported in over 100 countries (Table 1). All four of the dengue virus serotypes appear in Asia, Africa and the Americas. South-East Asia and the Western Pacific are the most seriously affected DF and DHF regions.

The incidence of dengue fever is rising in areas frequented by Canadian travellers. Central and South America and the Caribbean have seen increased prevalence since 1980. The current increases in prevalence in the Americas may be linked to growing urbanization and other social factors that aid mosquito reproduction. In Canada, there are between 40 to 50 cases of dengue confirmed by laboratory testing each year.

Symptoms
The illness begins with the sudden onset of flu-like symptoms including fever, headache, muscle aches and joint pain, pain behind the eyes and a faint rash. The fever usually lasts from three to five days, and rarely more than seven days.

While the disease is often mild and self-limiting, a more severe form -- dengue haemorrhagic fever -- can occur. Its symptoms include loss of appetite, vomiting, intense abdominal pain, shock and bleeding from the nose or under the skin. The occurrence of DHF may be associated with those either experiencing their second infection, being immuno-suppressed, or being under the age of 15. Dengue haemorrhagic fever can be fatal.

With respect to the four distinct but closely related DF virus serotypes, recovery from an initial infection caused by one strain provides lifelong immunity against that serotype only. There is good evidence that suggests that any subsequent reinfection by another strain of the DF virus increases your risk of acquiring the more serious disease, dengue haemorrhagic fever.

Treatment
There is no specific treatment for dengue fever or dengue haemorrhagic fever. Early medical intervention for dengue haemorrhagic fever may prevent serious illness.

Prevention and personal precautions
There is no vaccine that protects against the dengue virus. Using personal protective measures to prevent being bitten by an infected mosquito remains the only means to reduce your risk of exposure to the dengue virus.

Recommendations
Health Canada strongly recommends that travellers consult their private physician or a travel medicine practitioner to discuss their individual risk of exposure to dengue. If you are travelling to dengue-endemic areas, you should take the following personal precautions to reduce your exposure to day-time biting mosquitoes:

• remain in well-screened or completely enclosed, air-conditioned areas;
• wear light-coloured 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 greater than 50%, and there may be additional risk of toxicity with higher concentrations. New micro-encapsulated products containing 33% DEET are registered in Canada, and they should provide up to eight hours of protection.

Children and DEET
In rare instances, application of insect repellents with DEET has been associated with seizures in young children (only 14 cases 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. Therefore, for children, DEET in a concentration of 10% or less 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; and
• wash repellent-treated skin after children come indoors. If a reaction to insect repellent is suspected, wash treated skin and seek medical attention.

In Canada, DEET products are not recommended for use in children less than two years of age. For more information on insecticide use, go to http://hc-sc.gc.ca/pphb-dgspsp/publicat/info/repell_e.html.

Some things to think about...
If a fever develops within two weeks of leaving a dengue-endemic area, see a physician and indicate that you have recently travelled to tropical regions. As well, during or following travel to dengue-endemic areas, you should immediately report to a physician any fever that is associated with skin rash, bleeding or easy bruising, particularly if it occurs in children.

For more information...

• For International Reports of Dengue activity, visit the Travel Medicine Program's page at: http://www.hc-sc.gc.ca/pphb-dgspsp/tmp-pmv/df-dhf_e.html.
• For maps of dengue fever-endemic areas: visit the World Health Organization's online infectious disease section at http://www.who.int/ctd/dengue/geo.htm.
• General information about immunizations recommended for travel outside of Canada, visit the page at: http://www.hc-sc.gc.ca/pphb-dgspsp/tmp-pmv/236_e.html.
• More Know before you go! information, visit the page at: http://www.hc-sc.gc.ca/pphb-dgspsp/tmp-pmv/travel/advice_e.html.

Table 1: Countries or territories where dengue fever or dengue haemorrhagic fever is known to occur, 1975-1998 (2000*)
Region	Countries
Africa	Angola Burkina Faso Comoros Côte d'Ivoire Democratic   Republic   of Congo   (formerly   Zaire)	Djibouti Ethiopia Ghana Guinea Kenya Madagascar	Mauritius Mozambique Nigeria Réunion Senegal	Seychelles Sierra Leone Somalia South Africa Sudan	Tanzania,   United   Republic   of...
Americas & Caribbean	Anguilla Antigua and   Barbuda Argentina Aruba Bahamas Barbados Belize Bolivia Bonaire Brazil British Virgin   Islands	Colombia Costa Rica Cuba Curaçao Dominica Dominican   Republic Ecuador El Salvador French Guiana Grenada Guadeloupe	Guatemala Guyana Haiti Honduras Jamaica Martinique Mexico Montserrat Nicaragua Panama Paraguay Peru	Puerto Rico St. Kitts & Nevis St. Lucia St. Martin St. Vincent &   Grenadines Suriname Trinidad &   Tobago Turks & Caicos   Islands	United States Venezuela Virgin Islands
Middle East	Saudi Arabia
East Asia	China	Hong Kong	Macao	Taiwan
South Asia & South-East Asia	Bangladesh Brunei Cambodia	India Indonesia Laos	Malaysia Maldives Myanmar	Pakistan Philippines Singapore	Sri Lanka Thailand Vietnam
Western Pacific & Micronesia	American   Samoa Australia Cook Islands Fiji French   Polynesia	Guam Kiribati Marshall   Islands Micronesia Nauru New Caledonia	New Zealand Niue Northern   Mariana   Islands Palau	Papua New   Guinea Samoa Solomon   Islands Tokelau	Tonga Tuvalu Vanuatu Wallis & Futuna   Islands

* Listing is current to year 2000 for the Americas & Caribbean Region only. All other regions are current to 1998.

Sources for Table 1:
- Dengue haemorrhagic fever: diagnosis, treatment, prevention and control. (2^nd edition), World Health Organization (WHO), 1997
- Weekly Epidemiological Record, WHO, April 25,1997
- Weekly Epidemiological Record, WHO, June 19, 1998
- Weekly Epidemiological Record, WHO, September 4, 1998
- Pan American Health Association, Country Reports to PAHO, September 5, 2000