ENTERIC VIRUSES IN DRINKING WATER WELLS: RELATING GEOSCIENCES TO HUMAN HEALTH

One-half of groundwater related disease outbreaks are attributed to viruses, but the links between viral occurrence in groundwater and source and transport of contamination are not well understood. Virus transport and infectivity are thought to be partly related to geologic conditions. For example, viral infectivity in the subsurface is limited to about two years, thus time of travel in the groundwater system is of primary importance. Moreover, the source of viral contamination can be uncertain; fingerprinting the source of water to a well can provide insight into the sources of viruses.

Recent work related geologic conditions to the occurrence of enteric viruses in municipal well water from a sand-gravel aquifer in Wisconsin by characterizing the sources of water and time of travel to drinking-water wells. A groundwater model was used to select one river site and four municipal wells for study. The wells included ones that received low (one well), high (one well), and intermediate (two wells) levels of surface-water contributions via bank filtration. Sites were sampled monthly; surface water contributions and time of travel were determined from ¹⁸O/¹⁶O and ²H/¹H ratios of the water. Samples were analyzed for enteric viruses and microbial indicators of sanitary quality. Of 48 well samples analyzed for viruses by reverse-transcription PCR, 50% were positive. Through characterization of the sources of water to the wells, it was demonstrated that there was at least one other unidentified source responsible for the virus contamination in addition to the surface water source. Moreover, analyses of the time of travel to one well yielded estimates less than one year; this was consistent with a positive cell culture test for infectious hepatitis A virus at that well.

All of the 48 well samples tested negative for indicators of sanitary quality even though 50% of the well samples were positive for viruses. Other public health ramifications of this work are currently uncertain as the research objective called for sampling before chlorination. In on-going research, we are investigating sanitary sewers as a second source of virus contamination in addition to surface water at other sand and gravel aquifers. This work augments a larger epidemiology study on the health effects of viruses in drinking water currently underway.