An acute viral disease with fever, rash, lymphadenopathy, headache and extreme pain and stiffness in the joints that temporarily is completely incapacitating. The fatality rate, although not very high, is on the increase. The disease is distributed throughout the tropical and subtropical areas of the globe and has been reported in over 100 countries; worldwide, there may be up to 2 billion people at risk. All four of the dengue virus serotypes are circulating in Asia, Africa, and the Americas. They are cousins of the yellow fever microobe. There are currently no vaccines for preventing the acquisition of dengue fever.
Dengue fever is commonly spread by urban mosquitoes of the Aedes genus, and one of the most common vectors, Aedes aegypti, lives in close proximity to man. Increases in prevalence are believed to be related to increasing urbanization and other social factors that favour increased mosquito reproduction. While the disease is often mild and self-limiting, it may present in a severe form associated with haemorrhagic complications, shock, and, in some cases, death. This severe form is called dengue haemorrhagic fever (DHF). The name denga is Swahili.
The disease is spread by mosquitoes that breed in old tires and other water-holding junk in crowded urban environments, infects an additional 30 million to 60 million people each year. It may occur in any country where the mosquito carriers (mainly Aedes aegypti) breed. Outbreaks occur chiefly in Africa, India, the Far East, and also in Hawaii, the Philippines and Caribbean Islands, reaching a peak during the rainy season. Cases are found mainly in cities and towns, although there is a rise in the number of reported cases in rural areas. 90% of the victims are under 5 years of age.
A marked increase in cases of dengue fever has been observed over the past decade, especially in tropical and subtropical areas of Central and South America and the Caribbean. This increased activity has recently been associated with the re-emergence of one type of the virus that has not been observed in Central America for some time.
Demographic changes, in particular rapid, unplanned urbanization, have resulted in conditions that encourage the spread of diseases such as dengue fever. The two primary mosquito vectors of the dengue, Aedes aegypti and Aedes albopictus, have adapted from their natural forest environments, where they breed in tree holes containing rainwater, to the urban environment where they breed in drains, water cans, discarded tyres, pots and bottles (Gubler and Clark 1994).