Steven studies the transmission of human pathogens. He conducts field studies, analyses data and uses mathematical models to look at scientific questions that are relevant to public health. Prior to the pandemic, he worked mainly on outbreaks and influenza, with an interest in spatial transmission processes, contact patterns and complex exposure histories. During the COVID-19 pandemic, up to October 2021, he contributed through the Imperial College COVID-19 Response Team, the Scientific Pandemic Influenza - Modelling (SPI-M) committee and the Realtime Assessment of Community Transmission (REACT) study. Since October 2021, has been 90% seconded to the UK Health Security Agency as the Director General for Data Analytics and Surveillance.