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Dengue is a mosquito-borne infection which in recent years has become a major international public health concern. Dengue is found in tropical and sub-tropical regions around the world, predominatelyin urban and peri - urban areas. Dengue hemorrhagic fever (DHF), a potentially lethal complication, was first recognized during the 1950s and is today a leading cause of childhood mortality inseveral Asian countries. There are four distinct, but closely related, viruses which cause dengue. Recovery from infection by one provides lifelong immunity against that serotype but confers only partialand transient protection against subsequent infection by the other three. Indeed, there is good evidence that sequential infection increases the risk of more serious disease resulting in DHF
The globalprevalence of dengue has grown dramatically in recent decades. The disease is now endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, South-East Asia and theWestern Pacific. South-East Asia and the Western Pacific are most seriously affected. Before 1970 only nine countries had experienced DHF epidemics, a number which had increased more than four-fold by 1995.Some 2500 million people - two fifths of the world's population - are now at risk from dengue. WHO currently estimates there may be 50 million cases of dengue infection worldwide every year. In 1998alone, there were more than 616,000 cases of dengue in the Americas, of which 11,000 cases were DHF. This is greater than double the number of dengue cases which were recorded in the same region in1995. Not only is the number of cases increasing as the disease is spreading to new areas, but explosive outbreaks are occurring. In Brazil nearly 475,000 cases were reported between January and October1998 – more than were reported from the entire continent in previous years
Dengue viruses are transmitted to humans through the bites of infective female Aedes mosquitoes. Mosquitoes generally...