Info Dengue: a nowcasting system for the surveillance of dengue fever transmission

Abstract

This study describes the development of an integrated dengue alert system (Info Dengue), operating initially in the city of Rio de Janeiro, Brazil. It is a project developed as a partnership between academia and the municipal health secretariat. At the beginning of each epidemiological week, the system captures climate time series, dengue case reporting and activity on a social network. After data pre-processing, including a probabilistic correction of case notification delay, and calculation of dengue's effective reproductive number, indicators of dengue transmission are coded into four dengue situation levels, for each of the city's ten health districts. A risk map is generated to inform the public about the week's level of attention and the evolution of the disease incidence and suggest actions. A report is also sent automatically to the municipality's situation room, containing a detailed presentation of the data and alert levels by health district. The preliminary analysis of Info Dengue in Rio de Janeiro, using historical series from 2011 to 2014 and prospective data from January to December 2015, indicates good degree of confidence and accuracy. The successful experience in the city of Rio de Janeiro is a motivating argument for the expansion of Info Dengue to other cities. After a year in production, Info Dengue has become a unique source of carefully curated data for epidemiological studies, combining epidemological and environmental variables in unprecedented spatial and temporal resolutions.