David Walker is a molecular virologist in the Food Safety group at the Cefas Weymouth laboratory. After obtaining his PhD on the investigation of biofilm communities and their mitigation on environmental sensors, from Southampton University in 2012, he joined the food safety group at Cefas to carry out sanitary surveys for the bivalve shellfish production areas in England and Wales. This involved characterising sources and movement of faecal contamination sources to shellfish harvesting areas to inform monitoring for classification under regulation (EC) 854/2004. He then went back into the laboratory to develop methods for rapid assessment of faecal indicators in environmental waters and improvements for official control methods. David has several years of experience developing and implementing molecular biological methods for marine and aquatic environments, including laboratory analysis and field sampling.