Dengue dynamics in the 2009 outbreak in Oran, Argentina: Implications for monitoring and control

GIL, JF; PALACIOS, M; APARICIO, JP; MANGUDO, C; COPA, N; VILLALPANDO, C; JAIME, C; FLORES, R; ARIAS, L; CORTADA, P; NASSER, JR; KROLEWIECKI, AJ

Philadelphia

Encuentro; The American Society of Tropical Medicine and Hygiene, 60 th Annual Meeting; 2011

ASTMH

After more than eighty years Dengue reemerged in Argentina in 1997. Since then, the largest epidemic in terms of geographical extent, magnitude and mortality, was recorded in 2009. In this work we analyzed the space-time dynamic of the Dengue epidemic in Oran, Salta province, one of the main epicenters of the outbreak. We also studied its correlation with demographic, socioeconomic and entomological factors. The city of San Ramon de la Nueva Oran is located in one of the main route of introduction of Dengue to northwest Argentina. Cases were diagnosed by UM-ELISA and MAC-ELISA (IgM) between January and June 2009. Demographic and socioeconomic data by neighborhood were obtained from the Provincial Statistics Direction. Diagnosis date and place of residence of patients were entered on a Geographic Information System using vector format cartography and Gauss Kruger coordinates into ArcGIS 9.3 software. We applied a space-time scan statistic under Poisson model considering city neighborhoods as the spatial unit and day as the temporal unit. Spearman correlation was used to study associations between socioeconomic variables and Dengue incidence. Larval house (LH) and Breteau (B) indices of Aedes aegypti space-time distribution was smoothed by kernel density. The epidemic started from an imported case from Bolivia which generated two seminal clusters on February 26 and 27, in the northeast and the south of the city with risk ratios of 32.9 and 36.4 respectively (p <0.001). Following cases spread around the city without significant space-temporal clustering. No statistically significant association between socioeconomic variables and dengue incidence by neighborhood was found but positive correlation between population size and the number of cases (p<0.05) were detected. Larval indices show maximum values for the month of January (B=21.96; HL=8.39) with a gradual decrease until June. The lack of correlation between socioeconomic variables and incidence show that in this case socioeconomic conditions are not risk factors for Dengue transmission.