The transmission dynamics of human verocytotoxigenic Escherichia coli (VTEC) infections are not well understood. This thesis examines the transmission of VTEC, exploring the role of environmental conditions on the risk of primary infections, and the impact of person to person transmission during outbreaks. The first study explored the effect of environmental factors on VTEC infections in Ontario using case-crossover analyses. While the magnitude and direction of the effect was variable between health units, the findings demonstrate that infections were associated with hydrological conditions. The second study focused on the potential impact of person to person transmission using a mathematical model to describe an outbreak in Ontario. Based on the model results, including public health interventions targeting person-to-person transmission reduced the outbreak size by ~16%. The results from these studies demonstrate that watershed hydrology may be associated with VTEC infections, and that person to person transmission is an important transmission route to target for interventions during outbreaks.