Modeling gene sequence changes over time in type 3 dengue viruses from Ecuador.

Dengue virus (DENV) is a member of the genus Flavivirus of the family Flaviviridae. DENV-3 re-emerged in Central America in 1994, and continues to expand into the South American region. Little is known about the evolutionary rates, viral spread and population dynamics of this genotype in the Latin American region. In order to gain insight into these matters, we used a Bayesian Markov chain Monte Carlo (MCMC) approach, to analyze envelope (E) gene sequences of the DENV-3 genotype III of strains included in a monophyletic cluster composed by Ecuadorian as well as strains from Cuba, Puerto Rico and Peru. The results of these studies revealed that the expansion population growth model was the best fit to the data. The most common recent ancestor (MRCA) was placed around 1989, in agreement with the first reports of the emergence of this new DENV-3 type. A mean rate 1.033 x 10(-3) nucleotide substitution per site per year was obtained. This rate is comparatively higher than the ones obtained for DENV-2 and DENV-4 in the same region. Faster population growth and greater population dispersal may have contributed to the vigorous initial transmission dynamics of this genotype in the Latin American region.