Chen SP. Epi­demiol Infect. 14 May 2012. doi:10.1017/S0950268812000908.
Avail­able at http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8577682

Abstract. Thai­land was a hyper-endemic coun­try for dengue with co-circulation of four serotypes and tens of thou­sands of infected cases annu­ally. Tak­ing into con­sid­er­a­tion the large num­ber of local dengue virus (DENV) sequences avail­able in Gen­Bank, Thai­land was the most ideal local­ity to study co-evolution of DENV. There­fore, we under­took a large-scale mol­e­c­u­lar epi­demi­o­log­i­cal analy­sis of all DENV strains iso­lated in Thai­land. In this study, we demon­strated that DENV strains of four serotypes post-1990 grouped into dis­tinct clades, and that spe­cific muta­tions in the enve­lope pro­tein were first con­firmed in these clades. Com­pared to the DENV1, DENV2 and DENV3 clades, the DENV4 clade evolved markedly more slowly (6·4×10–5 substitutions/site per year). Our results also showed that the genetic diver­sity of the pre­dom­i­nant geno­type of each serotype tended to slightly increase over time with fluc­tu­at­ing changes, fol­lowed by a sta­tion­ary phase after 2000. This sug­gests that the four DENV clades became the pre­dom­i­nant strains due to DENV pos­sess­ing improved fit­ness after long-term selection.