HUMAN AND BOVINE VIRUSES IN URBAN AND RURAL STREAMS: HYDROLOGIC AND SEASONAL PATTERNS OF WASTEWATER INFLUENCE

Viruses are the cause of many waterborne diseases contracted from fecal-contaminated waters. Collection of samples that properly represent virus concentrations throughout relevant hydrologic periods has historically been difficult due to the large water volume collection and filtration required for virus analysis. For this study, a process control system was developed for unattended large-volume virus sample filtration over extended durations. Surface water was pumped at specified rates, and pH was monitored and modified to levels that optimize virus recovery within the filter. A pre-filter for large-solids and a glass-wool filter were used for virus capture. Internal pressure was monitored for assessment of filter blockage and a second filter was used when necessary. The system was programmed to begin and end sampling through telemetry and to collect flow- or time-weighted composite samples. Identification and quantitation of specific viruses were conducted by real time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and TaqMan probe. Inhibition levels to the RT-PCR reactions from elevated level of naturally occurring compounds in samples were evaluated with an inhibition control in every sample. Samples that were RT-PCR positive for enteroviruses and adenoviruses were analyzed for infective virions by integrated cell culture-PCR. Monitoring locations within the Milwaukee River system included an urban subwatershed, a rural subwatershed, and the Milwaukee River at the mouth. Results provided event-mean concentrations of viruses (6 human and 8 bovine). Sample volumes ranged from 56 to 2,800 liters of water for individual filters. Each human virus was detected at least once and 3 of 8 bovine viruses were detected in 18 months of data collection from three sampling locations. Human viruses were present in 63% of precipitation and snowmelt runoff samples, and 20% of low-flow samples. Bovine viruses were present in 46% of precipitation and snowmelt runoff samples and 14% of low-flow samples. Occurrence at individual monitoring locations varied from 40 to 61% for human and 35 to 50% for bovine viruses. Infectivity was confirmed in 24% of the adenovirus and enterovirus-positive runoff samples, while none of the low-flow samples were confirmed to be infective.