Chonticha KlungthongChunlin ZhangMammen P. MammenSukathida UbolEdward C. HolmesArmed Forces Research Institute of Medical Sciences, ThailandMahidol UniversityUniversity of Oxford2018-07-242018-07-242004-11-10Virology. Vol.329, No.1 (2004), 168-179004268222-s2.0-5144226152https://repository.li.mahidol.ac.th/handle/123456789/21345Dengue represents a major public health problem in Thailand, with all four viral serotypes co-circulating. Dengue virus serotype 4 (DENV-4) is the least frequently sampled serotype, although one that is often associated with hemorrhagic fever during secondary infection. To determine the evolutionary forces shaping the genetic diversity of DENV-4, and particularly whether its changing prevalence could be attributed to instances of adaptive evolution in the viral genome, we undertook a large-scale molecular epidemiological analysis of DENV-4 in Bangkok, Thailand, using both E gene and complete coding region sequences. This analysis revealed extensive genetic diversity within a single locality at a single time, including the discovery of a new and divergent genotype of DENV-4, as well as a pattern of continual lineage turnover. We also recorded the highest average rate of evolutionary change for this serotype, at 1.072 × 10-3nucleotide substitutions per site, per year. However, despite this abundant genetic variation, there was no evidence for adaptive evolution in any gene, codon, or lineage of DENV-4, with the highest rate of nonsynonymous substitution observed in NS2A. Consequently, the rapid turnover of DENV-4 lineages through time is most likely the consequence of a high rate of deleterious mutation in the viral genome coupled to seasonal fluctuations in the size of the vector population. © 2004 Elsevier Inc. All rights reserved.Mahidol UniversityImmunology and MicrobiologyArticleSCOPUS10.1016/j.virol.2004.08.003