Characterising dengue transmission intensity from seroprevalence and case notification data globally

Dengue is the mosquito-borne viral disease with the highest number of infections worldwide, with reported cases across 129 countries, and about half of the global population currently at risk of infection. The substantial increase in dengue incidence - 30-fold in the last decades – poses a substantial public global health challenge. With the recent introduction of Qdenga, the second licensed dengue vaccine, and the implementation of Wolbachia-carrying mosquitoes, increasing our knowledge on dengue transmission intensity worldwide is fundamental to understand the underlying dengue burden and assess the impact of these new interventions in the population. To achieve this, in this thesis, we used seroprevalence and case-notification data to estimate dengue force of infection (i.e. the per-capita risk of infection of a susceptible individual in a population) across several endemic countries. We began with a literature review aimed at collating previously published age-stratified seroprevalence datasets, which we then used to estimate the force of infection of different locations. Doing so, we noticed how dengue serosurveys remain limited on the African continent. Therefore, we designed a new simulation-based framework to determine the size and age distribution of blood samples in dengue serosurveys by leveraging existing blood samples, which can also be applied in resource-limited countries. We showed its application in three African countries where we designed a nested serological survey and analysed the multiple assays’ results to characterise dengue and other arbovirus transmission. Moreover, in this thesis we provided an example of how to study dengue transmission in those countries where dengue is a notifiable disease, by analysing a 7-year case notification dataset from Sri Lanka, and the potential climatic and socio-economic drivers of its transmission in the country. Overall, we believe this thesis increased our understanding of dengue transmission in several countries worldwide and have helped the implementation of new serosurveys and increased our knowledge of dengue and other arboviruses circulation in Africa. This work will help guiding the implementation of surveillance systems and targeting public health interventions, such as the newly licensed dengue vaccine together with recent vector-control strategies.