Study links viral GI illnesses to untreated wells

Jun 5, 2012 (CIDRAP News) – A study found that low-level viral contamination and a higher incidence of acute gastrointestinal (GI) illness were linked to nondisinfected municipal groundwater in Wisconsin, findings that researchers say could spur regulatory steps.

The investigators analyzed tap water samples and human illness patterns in 14 Wisconsin towns before and after ultraviolet (UV) disinfection systems were installed on community wells. Their study appeared in Environmental Health Perspectives.

Though numerous studies over the years have detected many human enteric viruses in groundwater, the public health significance hasn't been clear, according to the researchers. They noted that 147,333 of the nation's public water systems use groundwater, and 95,631 of them provide water without disinfection.

The work was conducted in 2006 and 2007 as part of the Wisconsin Water and Health Trial for Enteric Risk Study. During the first year, eight communities had low-pressure, UV disinfection reactors installed on all operating municipal wells. Researchers implemented a crossover intervention in the winter of 2006-2007, and the eight towns converted back to nondisinfected water while the wells in the six other towns got UV disinfection.

The team sampled water during 12-week surveillance periods, using quantitative polymerase chain reaction (qPCR) testing to detect viral RNA. Enteroviruses and adenoviruses were serotyped and evaluated for infectivity by cell culture. Households kept health diaries during the same periods.

Investigators found that both communities and periods with the highest virus measures were associated with higher levels of GI illnesses. The link was strongest for norovirus genogroup 1 and for adult enterovirus illnesses when echovirus subtypes were predominant.

They estimated that the percentage of illnesses linked to tap waterborne viruses was between 6% and 22%, depending on the incidence model used.  For children younger than age 5, researchers predicted that the percentage of illnesses linked to tap waterborne viruses could have been as high as 63% when noroviruses were abundant in the water.

They concluded that communities with nondisinfected groundwater systems may be at an increase risk for waterborne viral illnesses, most likely spread by wastewater leaking from sanitary sewers. The group also noted that groundwater-borne viruses are receiving greater scrutiny in a proposed rule that would authorize national monitoring for enterovirus and norovirus in nondisinfected public wells.

Borchardt MA, Spencer SK, Kieke BA, et al. Viruses in non-disinfected drinking water from municipal wells and community incidence of acute gastrointestinal illness. Environ Health Perspect 2012 Jun 1 [Abstract]

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