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A novel water quality intervention that consists of point-of-use water disinfection, safe storage and community education was field tested in Bolivia. A total of 127 households in two periurban communities were randomized into intervention and control groups, surveyed and the intervention was distributed. Monthly water quality testing and weekly diarrhoea surveillance were conducted. Over a 5-month period, intervention households had 44% fewer diarrhoea episodes than control households (P=0·002). Infants <1 year old (P=0·05) and children 5–14 years old (P=0·01) in intervention households had significantly less diarrhoea than control children. Campylobacter was less commonly isolated from intervention than control patients (P=0·02). Stored water in intervention households was less contaminated with Escherichia coli than stored water in control households (P<0·0001). Intervention households exhibited less E. coli contamination of stored water and less diarrhoea than control households. This promising new strategy may have broad applicability for waterborne disease prevention.

A field experiment was conducted on a Corolla fine sand (Aquic Quartzipsamment) to evaluate wastewater treatment by septic systems under conditions typical of Atlantic coastal barrier islands. The effects of loading rate and water table depth on wastewater treatment were studied. Two absorption fields were installed and were designated the upper and lower fields based on their relative topographic locations. The trenches in the lower field were 30 cm closer to the water table than the trenches in the upper field. Each field consisted of nine absorption trenches. Three loading rates (1, 4, and 16 cm d−1) were each replicated three times in a completely randomized design. Groundwater samples around the trenches were collected biweekly from shallow wells (1.5–1.9 m deep) between May 1982 and December 1983, and were analyzed for NO−3‐N, NH+4‐N, soluble P, Na+, Cl−, K+, and fecal coliform bacteria. During the first year the water table was within 30 cm of the lower field trenches 20% of the time, and anaerobic conditions prevailed. Groundwater samples collected adjacent to the trenches contained predominantly NH+4‐N, fecal coliform counts averaged over 25 000 MPN (most probable number) L−1, and the redox potential averaged <300 mV. During the second autumn the lower field showed aerobic tendencies due to drier weather and a deeper water table. The upper field remained aerobic throughout, with almost complete nitrification occurring. Average fecal coliform counts were reduced to 60 MPN L−1, and the mean redox potential was >500 mV. The wastewater loading rate had a significant effect on the levels of all constituents, but the loading rate effect was smaller than the water table effect. Phosphorus movement appeared to be related to pore‐water velocity.

A reverse transcriptase (RT)-polymerase chain reaction (PCR)-oligoprobe (OP), or RT-PCR-OP, method was developed for the detection of the Norwalk virus, which causes acute, epidemic gastroenteritis, in stool specimens. The Norwalk virus genome regions encoding the following two proteins were amplified by RT-PCR: the RNA polymerase (260-bp product) and a putative immunogenic protein (224-bp product). The resulting DNA fragments (amplicons) were hybridized to a digoxigenin-labeled internal OP specific to each amplicon. The detection limit of Norwalk virus, as determined by the endpoint of RT-PCR amplification for serially diluted, positive stool specimens, was similar to the actual virion titer as estimated by electron microscopy and at least 100-fold greater than the titer determined by radioimmunoassay (RIA). The RT-PCR-OP assay was specific for Norwalk virus and negative for other enteric viruses, including human and animal caliciviruses, hepatitis E virus, Snow Mountain agent, astroviruses, 16 human enteroviruses, and 5 human rotaviruses. Components of fecal specimens that interfere with RT-PCR were removed successfully by Sephadex G-200 gel chromatography. Of 20 stool specimens from human volunteers that were positive for Norwalk virus by RIA, a specific RT-PCR-OP result was obtained in 95% (19 of 20) of the samples by using the immunogenic protein primers and 75% (15 of 20) by using the polymerase primers. Twenty-six stool specimens from asymptomatic children and adults were negative by the Norwalk virus RT-PCR-OP. RT-PCR-OP detected Norwalk virus in the 4 of 21 coded fecal specimens that were also positive by enzyme immunoassay. Two samples that were positive by RIA or enzyme immunoassay were negative by RT-PCR, perhaps because viral RNA was not present or RT-PCR inhibitors were not adequately removed.