The largest dengue outbreak in Argentina and spatial analyses of dengue cases in relation to a control program in a district with sylvan and urban environments

AE CARBAJO; RUBIO, ALEJANDRA; MARIA JOSÉ VIANI; MARÍA ROXANA COLOMBO

Asian Pacific Journal of Tropical Medicine

Hainan Medical College

Año: 2018 vol. 11 p. 227 - 234

1995-7645

Objective: To analyze the largest outbreak of dengue in Argentina in the municipality of Tigre during 2016, through detailed spatial analyses of the occurrence of cases in relation to demographic factors and vector control actions. Methods: Detailed and georreferenced dataon dengue cases with laboratory results (NS1 or IgM) were analyzed. The occurrences ofimported and autochthonous cases by census tract were modeled using demographic variables(population by age class, proportion of foreigners, proportion with university grade, proportionof males), dwelling variables (number of homes, proportion of dwellings with latrine, numberof dwellings, proportion of houses, proportion of flats, proportion of slums) and census tractarea as explanatory variables. The probability of occurrence of autochthonous and importedcases was modeled separately. The spatio-temporal occurrence of cases was studied in relationto focal and perifocal control actions (involving education campaigns, removal of Aedesaegypti breeding sites and exhaustive insecticide spraying) to assess the efficiency in stoppingautochthonous cases spreading. Results: All autochthonous cases occurred in the urbanenvironment with no sylvan cases. The majority of the imported cases registered came fromParaguay and Northeastern Argentina. The age structure of imported and autochthonous casesdid not differ from the age structure of the municipality, while that of the negative cases did.When studied spatially, the occurrence of imported cases by census tract was mildly associatedwith a higher proportion of foreign population and more people at active age, while occurrenceof autochthonous cases was not significantly associated with any of the studied variables.For census tracts with laboratory confirmed results, the models showed higher probability ofautochthonous cases related to higher population density and population age structure. Theclustering of autochthonous cases was generally mild, with prevailing isolated cases and aweak spread inside the municipality. The biggest outbreak focus was associated with a delayin the focal vector control. Conclusions: Results confirmed the virus pressure coming fromneighboring countries and related to population movement by workers. All autochthonouscases occurred in the urban environment with no sylvan cases. The susceptibility of residentsto dengue may be similar among age classes and the laboratory tests were performed morefrequently in the younger. Autochthonous cases incidence was low and spatio-temporalclustering of cases weak, suggesting that control measures were effective when no delayoccurred in their application.