enteric pathogens. Initially there were only a few anecdotal reports of transmission by contaminated water in the literature (Kurtz and Lee, 1987). More recently, large outbreaks and the importance of astroviruses have been recognized, and evidence for waterborne transmission is mounting (Abad et al., 1997). Enteric adenoviruses (serotypes 40 and 41, also known as subgenus F) are DNA viruses that are a common cause of pediatric diarrhea. Although adenoviruses have been recovered from sewage (Foy, 1991), there has been no evidence of drinking water waterborne transmission, though recreational outbreaks have been reported (Crabtree et al., 1997).
Coronaviruses were first observed in feces of persons with gastroenteritis by electron microscopy in 1975, but since then they have also been frequently detected in the feces of healthy people; their etiologic role in human diarrhea remains doubtful. Epidemiologic evidence suggests that fecal-oral transmission and personal hygiene may be key factors in transmission since several studies have noted that the highest prevalence rates were among populations with poor personal hygiene (Caul, 1994).
Toroviruses, which are well-established enteric pathogens of cattle and horses, have been found in stool samples from children and adults with diarrhea (Koopmans et al., 1991, 1993) but have remained unconfirmed as human pathogens. Similarly, picornavirus and pestivirus have been detected in fecal specimens from adults and children with diarrhea, but their clinical significance is not known.
The pathogenic bacterium Helicobacter pylori, formerly referred to as Campylobacter pylori, causes indigestion and abdominal pain, and chronic infection may result in peptic ulcers and gastric cancer. H. pylori infections occur throughout the world, and the prevalence of infection increases with age. Fecal-oral transmission of H. pylori infection has been suggested by several studies that implicated crowding, socioeconomic status, and consumption of raw, sewage-contaminated vegetables as risk factors for infection (Hopkins et al., 1993; Mendall et al., 1992; Mitchell et al., 1992). Studies in Peru have identified type of water supply (municipal vs. community wells) as a risk factor for infection with H. pylori and found that water source appeared to be a more important risk factor than socioeconomic status; children from high-income families who received their water from the Lima municipal water supply, which comes from a surface water source, were 12 times more likely to become ill than high income children who drank well water, with community wells posing a higher risk than treated municipal supplies (Klein et al., 1991). Yet a seroprevalence survey of 245 healthy children in Arkansas found no relation between H. pylori seropositivity and type of water supply (municipal or well) (Fiedorek et al., 1991). However, the levels of fecal contamina-