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Phages infecting human-associated Bacteroides fragilis (GB-124 phages) have been employed in the European Union (EU) to identify human faecal pollution, but their utility for the United States was unclear. Primary sewage samples were collected seasonally from seven wastewater treatment plants (WWTP) across the continental United States, and more time-intensive sampling was conducted at local WWTPs. All samples were assayed for plaque-forming units (PFU) of GB-124 phages, somatic and FRNA-specific coliphages, as well as adenoviruses (by quantitative PCR [qPCR]). Animal faecal samples (>250) from 14 different species were tested for the presence of the three phage groups. GB-124 phages were consistently detected in sewage (10-102PFUml-1), but not in animal faeces. While density estimates of both coliphages in sewage were approximately one order of magnitude higher than GB-124 phages, they were both randomly detected in animal faecal samples (102-105g-1 dry weight). Stability of all three phages was inversely proportional to temperature; persistence was greatest at 5 degrees C compared to 20 and 35 degrees C, where no phages were detectable after a week. In summary, GB-124 phages appear to be a feasible alternative indicator organism and benefit from being sewage associated, while providing an inexpensive detection technique for infectious virions.