The microbiology of urban UK floodwaters and a quantitative microbial risk assessment of flooding and gastrointestinal illness

A quantitative microbial risk assessment of flooding and gastrointestinal illness was carried out using a combination of floodwater quality data from the existing literature on pathogen concentrations in the various floodwater components, the use of microcosms to determine pathogen die-off rates in floodwaters and opportunistic sampling of actual UK floodwaters. Two flood-related scenarios were examined in a hypothetical population to provide an assessment of the likely cases of gastrointestinal illness resulting from contact with floodwater. The results of the study suggest that significant numbers of people are at risk of illness (especially from viral gastroenteritis) during the clean-up process rather than during the inundation and withdrawal phases. Additional sampling during flood events of water and sediment would strengthen the empirical policy evidence base required for estimating the severity and range of health impacts using the risk assessment methodology developed in this paper.