Detection of four dengue serotypes suggests rise in hyperendemicity in urban centers of Brazil

FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo) 2010/19059-7FAPESP 2011/17071-2 and 2013/10382-8CNP

Epidemiological dynamics of an urban Dengue 4 outbreak in São Paulo, Brazil

Background: Dengue studies at the urban scale are scarce and required for guiding control efforts. In Brazil, the burden of dengue is high and challenges city public health administrations with limited resources. Here we studied the dynamics of a dengue epidemic in a single city. Methods: Serum samples from dengue suspected cases were collected and tested, from December 2012 and July 2013 in Guarujá, Brazil. We use incidence series analysis to provide a detailed view of the reproduction number dynamics and a Bayesian analysis to infer the spread of the serotype using geographic and temporal data. Results: We obtained nucleotide sequences from 354 envelope genes and georeferenced 286 samples during the course of the outbreak. Serotype 4 was responsible for the epidemic. We identified at least two major lineages that overlapped in distribution. We observed high reproduction numbers and high cladogenesis prior to the escalation of clinical case notifications. Three densely populated non-adjacent neighborhoods played a pivotal role during the onset and/or course of the epidemic. Discussion: Our findings point to high dengue virus transmission with a substantial proportion of unapparent cases that led to a late recognition of an outbreak. Usually source reductions initiatives tend to be insufficient once an epidemic has been established. Nevertheless, health authorities in Guarujá prioritized vector control on specific places with clusters of georeferenced viremic patients, which appear to have diminished the epidemic impact

Maximum credibility tree (and its four serotype subtrees) showing the evolutionary relationships among the capsid/premembrane junction sequences of 55 strains.

<p>Posterior probability support values are shown over the nodes and TMRCAs values below the nodes. Reference sequences abbreviated by serotype (D1–4), genotype (<i>Am</i>: American, <i>AmAs</i>: American/Asian, <i>As</i>: Asian, <i>Cosm</i>: Cosmopolitan, <i>Syl</i>: Sylvatic, <i>I</i>, <i>II</i>, <i>III</i>, <i>IV</i>, or <i>V</i>), GenBank accession, ISO code for country, and isolation year.</p