Undocumented Burden of Dengue in Africa

Abstract

In Africa, information on dengue burden in Africa is limited. Dengue diagnostics is also a key challenge in defining the true burden. Among the various diagnostic options, rapid diagnostic test (RDT) is a convenient and prompt tool for dengue diagnosis, especially in resource-limited environments. To assess current knowledge on the use of RDTs for dengue with respect to their economic impact, a systematic review was conducted of published data. Overall, data were limited to demonstrate an economic impact of dengue RDTs and the available two studies reached different conclusions: one concluded that one particular RDT would be a cost-effective tool in endemic setting, and the other, based on a modeling, showed that a dengue RDT would not be advantageous in terms of cost and effectiveness compared to current practice of antibiotics prescription for undifferentiated fever. This thesis presents patterns of dengue epidemiology and outbreak based on passive fever surveillance studies in Mombasa, Kenya, and Ouagadougou, Burkina Faso. To estimate the proportion and understand clinical patterns of dengue-positive cases among non-malarial febrile patients, we conducted passive health facility-based fever surveillance studies in Ouagadougou, Burkina Faso and Mombasa, Kenya. In Mombasa, of 482 non-malarial febrile patients, 223 (46%) were identified as dengue– confirmed and 92 (19%) as dengue-probable. The surveillance covered the beginning of a dengue outbreak in April-May 2017, during which 67% of enrolled patients were dengue-confirmed. In Ouagadougou, of 2929 non-malarial febrile patients, 540 (18%) were identified as dengue–confirmed and 571 (19%) as dengue-probable. During the study period, a dengue outbreak occurred in September-November 2016, during which 46% of enrolled patients were dengue-confirmed. To understand DENV transmission in the community, 4 repeated serosurveys were conducted among the same individuals at 6 month intervals in Ouagadougou. Seroprevalence at enrollment was 66%. The binomial regression based on IgG positivity by age, assuming constant force of infection (FoI) over calendar time, resulted in the FOI of 6% per year. In summary, in both Burkina Faso and Kenya, there is considerable transmission of DENV, in terms of proportion of DENV confirmed infections among iii non-malarial febrile patients in the healthcare facilities as well as seroprevalence and FoI in the community. These burden estimates can facilitate evidence-based decision making on interventions for dengue prevention and control, including a dengue vaccine. However, given the currently available information on dengue burden in Africa and the status of dengue vaccine development, including the only licensed vaccine with restrictions in public health use, consideration of dengue vaccine introduction may be premature for Africa and more data would be necessary to build evidence base on dengue in African settings.