Human adenoviruses as waterborne index pathogens and their use for Quantitative Microbial Risk Assessment

The current microbial water quality standards are based on the monitoring of fecal indicator organisms, which are mainly bacterial indicators (i.e., Escherichia coli, intestinal enterococci), however epidemiological data indicate that viruses are important etiological agents of waterborne illnesses. Amongwaterborne viruses, human adenovirus can be considered as an index pathogen, owing to its abundance in sewage and persistence in the environment, as well as its potential infectivity. In this study, data on human adenoviruses from different watermatrices (the entrance and exit of awater treatment plant, rivers and seawaters)were analyzed, in parallel with traditional fecal bacterial indicators and somatic coliphages. The results showed a 64% frequency of positive adenovirus samples, decreasing fromthe sewage system(100% at the entrance and 94% at the exit) to rivers (92% and 72% for different rivers) and seawater (21%). Adenovirus concentrations showed a significant correlation with somatic coliphages in one river and seawater, thus supporting the recent inclusion of coliphages as viral indicators inwater safety guidelines. The data collected were used to estimate adenovirus to indicator ratios,which could be used as input in Quantitative Microbial Risk Assessment (QMRA) studies.