Dengue virus is a flavivirus transmitted by the mosquito Aedes spp.and is the causative agent for an increasing public health problem in tropical areas over the world, with almost 3.000 million people at risk of infection. Dengue virus produces a broad spectrum of symptoms, varying from a mild flu-like illness called dengue fever, to a severe and some times fulminating haemorrhagic fever disease with shock. Genetic caracterization of distinct virus serotypes allow us to understand the epidemiological patterns of distribution as well as to demonstrate the presence of specific haemorrhagic strains causing very severe disease and death. In this report, we have determined the evolutionary origins of Dengue Virus Type 2 circulating in Colombia before and after the first reported haemorrhagic fever case at the ends of 1989, by means of sequence and further analysis of a 240 pb PCR amplified fragment from the E/NS1 joining region; with the sequences obtained from 5 strains isolated before 1989 and 10 from strains isolated years after, a phylogenetic tree was constructed which showed the presence of 2 different genotypes in our country; comparison with strains previously isolated from around the world determined that one of the genotypes found corresponds to the native American genotype circulating before the appearance of haemorrhagic fever, while the later isolated strains of the second genotype belonged to a Southeast Asian genotype, suggesting displacement of the native strains by more virulent genotypes.
