Occurrence of Viruses in US Groundwaters

US groundwater may be subjected to fecal contamination from a variety of sources. This study sought to develop a preliminary assessment database on virus occurrence in groundwater systems at the national level. Information on physical and geological characteristics of groundwater wells, along with various microbial and physicochemical water quality parameters, was collected, and possible correlation with the presence of human viruses was investigated. Groundwater samples from 448 sites in 35 states were collected and assayed for microorganisms and chemical contaminants. Infective viruses, viral nucleic acid, bacteriophages, and bacteria were present in 4.8, 31.5, 20.7, and 15.1% of samples, respectively. Statistical analysis showed that one‐time sampling is not sufficient for proper risk characterization. No significant direct correlations existed between the presence of virus and microbial indicators. However, when only the sites with repeat sampling were examined for correlations between indicators and pathogens, it was observed that if a site tested positive for a microbial indicator, it also tested positive at some point in time for pathogens.