Outbreaks caused by four types of the dengue fever virus have increased in the past 25 years. About 40% of the world’s population lives in areas where there is a risk of dengue fever. Dengue fever is the most common viral disease spread to humans by mosquitoes. It can cause severe flu-like symptoms. In some cases it leads to dengue haemorrhagic fever, which can be fatal. There is no vaccine or medication that protects against dengue fever. The Public Health Agency of Canada (PHAC) recommends that travellers protect themselves from mosquito bites when travelling to areas where dengue fever may occur.