Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/31/2012
Publication Date: 9/1/2012
Citation: Borchardt, M.A., Spencer, S.K., Kieke, B.A., Lambertini, E., Loge, F.J. 2012. Viruses in non-disinfected drinking water from municipal wells are related to community rates of acute gastrointestinal illness. Proceedings of the National Academy of Sciences. 120:1272-1279. Interpretive Summary: Many public water systems in the United States are supplied by groundwater that is not disinfected. The water systems are located primarily in rural areas and include small towns, restaurants, motels, campgrounds, and schools. Waterborne disease outbreaks are not uncommon in the USA and more often than not the outbreaks happen in these small groundwater-supplied systems. Outbreaks are relatively easy to notice and measure. Sporadic illnesses, which have symptoms just as severe as outbreaks but are more difficult to detect because fewer people become ill at the same time, are suspected from drinking non-disinfected groundwater, but this has never been shown. In this study we found the municipal tap water of 14 rural Wisconsin communities to be contaminated with human pathogenic viruses. Of the 1,204 water samples collected, 24% were positive for one or more virus types. These viruses cause vomiting and diarrhea in adults and children, and, indeed, we were able to relate the average concentration of viruses in the communities’ tap water to sporadic gastrointestinal illnesses reported by people living in the communities. In other words, the higher the concentration of viruses at household taps, the more illnesses we observed in that community. The virus concentration did not need to be very high to observe an illness effect. We developed models relating measurements of the viruses to illness rates and were able to calculate that the proportion of the gastrointestinal illness in the communities that was attributable to drinking non-disinfected groundwater was about 10%. The study findings are notable on several counts. The viruses were measured using new state-of-the-art methods for quantifying viral DNA or RNA because for many virus types no other detection methods are available. Finding significant relationships between virus measures and illness rates means these new methods, which are less expensive and labor-intensive than conventional approaches, have value for determining public health risk. Moreover, using the models we developed, other scientists will be able to evaluate whether viruses found in a different environmental setting pose a risk to public health. Lastly, our study provides the first estimate on the number of sporadic gastrointestinal illnesses in the USA that are linked to drinking non-disinfected groundwater.
Technical Abstract: Groundwater supplies for drinking water are frequently contaminated with low-levels of human enteric virus genomes, yet evidence for waterborne disease transmission is lacking. We related qPCR-measured enteric viruses in the tap water of 14 non-chlorinating communities in the U.S. to acute gastrointestinal illness incidence (AGI) obtained through active surveillance. The communities and time periods when virus measures were highest had correspondingly high AGI. Tap water noroviruses and echoviruses increased AGI relative risk by 29% and 55%, respectively, at one genome/liter mean concentration. The AGI fraction attributable to waterborne noroviruses was as high as 29%. The majority of groundwater-source public water systems in the U.S. produce water without disinfection, suggesting the population served is exposed to waterborne viruses and the consequent health risks.