PhD ceremony Ms. Z.I. Velasco: Dengue in Venezuela. A study on viral transmission, risk factors and clinical disease presentation

Dengue has become the most important mosquito-borne viral disease worldwide. Epidemics of increasing magnitude regularly occur in Venezuela. In this thesis, approximately 2000 individuals belonging to three neighbourhoods of high dengue incidence in Maracay, Venezuela, were studied through a prospective community-based cohort study. The aims of this study were to determine the dengue seroprevalence, to identify risk factors for dengue infection and to recognize areas of high dengue transmission at block and household level through spatial analysis. Additionally, a health center-based observational cohort study was established to identify clinical and haematological parameters that discriminate dengue from other febrile illnesses (OFI) at an early stage of the disease. Early diagnosis is also influenced by health-seeking behaviour (HSB) and access of patients to care. We studied the patterns of HSB at the community level. We found a high dengue seroprevalence (77%) with 10% recent infections. The combination of increasingly crowded living conditions, growing population density, precarious homes and water storage are factors that likely determine dengue transmission. Through spatial analysis, clusters of high dengue transmission at block and household levels were found for recent dengue infections, but not for past infections. Our results also suggest that dengue transmission is highly focal and peridomestic. We constructed a diagnostic algorithm using white blood cells count, rash, mean corpuscular haemoglobin levels and haemorrhagic manifestations in sequential order that distinguished dengue from OFI during the first three days of the illness. Finally, we observed that intended pathways to seek care for suspected dengue differ from those in the case of other febrile illnesses.

Dissertation: http://irs.ub.rug.nl/ppn/384059090