Laura Espinosa is an Epidemic Intelligence Expert at the European Centre for Disease Prevention and Control (ECDC). In October 2020, ECDC developed an R-based open-source tool, epitweetr, for early detection of public health threats using Twitter data. In this session, attendees learned the process behind building such open-source R package for real-time monitoring of Twitter, understood the main functionalities of epitweetr, learned how to modify existing R packages locally and how to apply epitweetr functions to other case studies.