1. 8. Dengue virusThe causative agent of dengue disease is dengue virus (DENV), a group of four closely related but antigenically distinct flaviviruses. They are hypothesized to have evolved independently of ancestral sylvatic viruses between 100 and 1,500 years ago (Wang et al., 2000). The four groups are known as serotypes and referred to as dengue virus type 1 (DENV-1), dengue virus type 2 (DENV-2), dengue virus type 3 (DENV-3), and dengue virus type 4 (DENV -4). 1. 8. 1. TaxonomyThere are three genera in the family Flaviviridae (formerly known as group B arboviruses), namely Flavivirus, Pestivirus and Hepacivirus. Dengue virus is a member of the Flavivirus genus which includes 55 identified viral species (ICTVdB, 2006). The word Flavi is a derivation from the Latin “flavus” meaning “yellow” and the type species of the genus is a yellow fever virus (YFV). Flaviviruses get their name because of the jaundice seen in yellow fever patients. Many flaviviruses are important human pathogens, particularly dengue virus, yellow fever virus, Japanese encephalitis virus (JEV), West Nile virus (WNV), and tick-borne encephalitis virus (TBEV). Flaviviruses are mainly transmitted by mosquitoes and ticks, while for some no vector is known. Dengue was one of the groups classified when early researchers serologically divided the flaviviruses into eight antigenic complexes using cross-neutralization tests. However, many viruses, for example the prototype YFV genus, could not be affiliated with any complex (Calisher et al., 1989). As sequence data became available, phylogenetic inference from molecular data showed agreement with the antigenic complex classification. Plus, he revealed the... middle of the paper... his viral suitability. Most mutations in DENV genomes are deleterious and play an important role in the evolution of DENV. Another important factor for the adaptation of DENV is the diversification related to transmission in various geographic regions. Four dengue virus serotypes can cocirculate in endemic areas because immunity to one serotype does not protect against infection by heterologous serotypes. This is likely the result of selection driven by the restrictive effects of cross-protective antibodies produced against heterologous serotypes. Dengue virus strains that manage to escape this neutralization process have a significant competitive advantage and become the dominant lineages. This evolutionary adaptation not only allowed the cocirculation of all 4 serotypes, but also has a major influence on their pathogenicity for humans.