Gertjan Medema is chief science officer and principal microbiologist at KWR Watercycle Research Institute and part-time chair on Water & Health at Delft University of Technology. He has a MSc in Microbiology and PhD on Cryptosporidium and Giardia in water supply. The focus of his research in the past 27 years (80 publications) is the transmission of pathogenic micro-organisms via the environment and the effectiveness of barriers against pathogens. The objective is to provide a scientific basis for effective management of pathogen risks by the water sector. He coordinates the Joint Research Programme of the Dutch water utilities (BTO) and the research strategy at KWR.