Molecular epidemiology of dengue virus serotypes 2 and 3 in Paraguay during 2001-2006: the association of viral clade introductions with shifting serotype dominance.

To determine the genetic variability of dengue viruses (DENVs) in Paraguay, the complete envelope gene was sequenced for 4 DENV-2 and 22 DENV-3 strains isolated from 2001 to 2006. The sequence data were used in Bayesian phylogenetic analyses, which revealed that Paraguayan DENV-2 strains fell into two distinct clades within the American/Asian genotype, thus suggesting that the introduction of a new DENV-2 clade was likely associated with the shift of dominant serotype from DENV-3 to DENV-2 in 2005 and might have caused an outbreak of DENV-2. This study also indicated that DENV-3 strains fell into genotype III, of which, several 2006 isolates varied from the remaining isolates in their tree locations. The introduction of this new clade was likely associated with the shift of dominant serotype from DENV-2 to DENV-3 in 2006 and might have caused an epidemic of DENV-3. More data are needed to test this hypothesis.