Co-circulating serotypes in a dengue fever outbreak: Differential hematological profiles and phylogenetic relationships among viruses

- Dengue virus serotypes 1 (DENV1) and 3 (DENV3) co-circulated in Marília during 2007.
- Hematological profiles of patients infected by different serotypes were similar.
- Percentage of atypical lymphocytes could be associated to less platelets in DENV1.
- Percentage of atypical lymphocytes could be associated to severe leucopenia in DENV3.
- Apparently, DENV1 was introduced into Marília from northern Brazil.

BackgroundDengue virus, represented by four distinct, genetically diverse serotypes, is the etiologic agent of asymptomatic to severe hemorrhagic diseases. The spatiotemporal dynamics of dengue serotypes and its association to specific diseases vary among the different regions worldwide. By 2007, and in São Paulo State, Brazil, dengue-case concentration in urban centers had changed to increased incidence in small- and medium-sized towns, the case of Marília.ObjectivesThe aim of this article was to distinguish dengue serotypes circulating during the 2007 Marília outbreak and define their association to demographic and hematological patient profiles, as well as the phylogenetic relationships among the different viruses.Study designPCR amplicons corresponding to the junction of capsid and dengue pre-membrane encoding genes, obtained from dengue serologically positive patients, were sequenced. Hematological and demographic data of patients with different Dengue serotypes were evaluated by univariate and bivariate statistics. Dengue PCR sequences were used in phylogenetic relationships analyzed for maximum parsimony.ResultsMolecular typing confirmed co-circulation of the dengue serotypes 1 (DENV1) and 3 (DENV3), which presented divergent correlation patterns with regard to hematological descriptors. The increase in atypical lymphocytes, a likely indication of virus load, could be significantly associated to a decrease in leukocyte counts in the DENV3 group and platelet in the DENV1. Phylogenetic reconstitution revealed the introduction of DENV1 from northern Brazil and local divergence of DENV3 by either microevolution or viral introduction from other geographical regions or both.ConclusionsDengue dynamics showed regional molecular-epidemiologic specificity, which has important implications for introduction of vaccines, disease management, and transmission control.