The seriousness of epidemic dengue occurred at Paranavaí, PR, during the 2012-2013 summer was marked by the high number of disease registries, when more than 10% of population was diagnosed. That region is characterized by social and environmental conditions (climatics and urban ecological) which are propitious to vector Aedes aegypti proliferation. This research evidences the procedures performed by health professionals in order to reveal the fundamental factors to the epidemic consolidation. Several data were obtained as case records, insecticide use and home visits, as well a semi-structured interview with professionals from the municipality. It was verified that the main factors responsible for the severity of the epidemic were the unpreparedness of health professionals, the surveillance work interruptions during the electoral campaign in 2012, and the