Community intervention trial for estimating the risk of acute gastrointestinal illness from groundwater-supplied non-disinfected drinking water

Authors: Borchardt, Mark; KIEKE, BURNEY - Marshfield Clinic Research; Spencer, Susan; LAMBERTINI, ELISABETTA - Global Alliance For Improved Nutrition (GAIN); Burch, Tucker; LOGE, FRANK - University Of California

Submitted to: Journal of Water and Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2023
Publication Date: 8/16/2023
Citation: Borchardt, M.A., Kieke, B.A., Spencer, S.K., Lambertini, E., Burch, T.R., Loge, F.J. 2023. Community intervention trial for estimating the risk of acute gastrointestinal illness from groundwater-supplied non-disinfected drinking water. Journal of Water and Health. https://doi.org/10.2166/wh.2023.071.
DOI: https://doi.org/10.2166/wh.2023.071

Interpretive Summary: Drinking water for many rural communities in the United States comes from groundwater. Communities that rely on lakes or rivers for drinking water are required by federal law to use disinfection, but that is not the case for groundwater-supplied communities. Many of these communities do not disinfect their drinking water. A key question in the study of infectious diseases is what are the sources of disease transmission? For example, how much illness comes from food, person-to-person, pets, livestock, and water? In studying Wisconsin communities that use non-disinfected groundwater for drinking water, we found that in some time periods approximately 20% of stomach illness (vomiting and diarrhea) in children less five years old is from their drinking water. Many of the communities’ groundwater wells were contaminated with human viruses, some of which cause stomach illness. For adults living in the study communities between 10% and 18% of their stomach illnesses came from drinking non-disinfected groundwater. Understanding the sources of disease transmission and how much each source contributes to the disease burden is important for preventing illness and improving public health.

Technical Abstract: Approximately 85,000 public water systems are supplied by non-disinfected groundwater in the United States. Non-disinfected drinking water has been linked to disease outbreaks, but its role in sporadic illness is poorly understood. We studied 14 non-disinfecting groundwater-supplied communities and previously reported on sporadic acute gastrointestinal illness (AGI) as related to distribution system breaches and virus-contaminated tap water. Here, we focus on the communities’ groundwater supplies and risk for sporadic AGI. We conducted a community intervention trial with ultraviolet (UV) disinfection installed on all supply wells of intervention communities. In control communities study participants continued to drink non-disinfected groundwater. UV disinfection units were switched from intervention to control communities halfway through the study (i.e., crossover design). AGI incidence for intervention and control communities was estimated from 621 households (1,659 participants) completing weekly health diaries during four 12-week surveillance periods. Well water samples collected monthly were analyzed for enteric viruses by qPCR. There was no evidence for groundwater-borne AGI using the cross-over design. However, the types, serotypes, and infectivity of viruses in the groundwater-supply wells varied by surveillance period, suggesting exposure to groundwater-borne viruses was not constant. As an alternative analysis, we compared AGI incidence between intervention and control communities during the same surveillance period. During period 1, when norovirus genogroup I contaminated wells, estimates for AGI attributable risk percent from drinking non-disinfected groundwater ranged from 19% to 21% for children < 5 years old and 15% to 18% for adults. During Period 3, echovirus 11 contaminated wells and 10% of adult AGI was attributable to groundwater. Enteric virus contamination of groundwater is temporally variable. When contamination occurs, drinking non-disinfected groundwater can be responsible for a measurable fraction of AGI.