First do no harm: making oral rehydration solution (ORS) safer in a cholera epidemic Daniels N, Simons L, Rodrigues A, Gunnlaugsson G, Forester T, Wells J, Hutwagner L, Tauxe R and Mintz E Abstract Oral rehydration solution (ORS) is lifesaving therapy for cholera and pediatric diarrhea. During a cholera epidemic in Guinea-Bissau, we evaluated the microbiologic quality of ORS prepared at a hospital and tested a simple intervention using special vessels for disinfecting tap water with bleach and for preparing, storing, and dispensing ORS. Few coliform bacteria and Escherichia coli were recovered from tap water; however, pre-intervention ORS contained numerous bacteria including E. coli and toxigenic Vibrio cholerae O1. In contrast, ORS samples from intervention vessels had few or no coliform bacteria, no E. coli, and no V. cholerae. Mean pre-intervention counts of coliform bacteria (3.4 X 107 colony-forming units [cfu]/100 ml) and E. coli (6.2 X103 cfu) decreased significantly during the intervention period to 3.6 X 102 cfu and 0 cfu, respectively (P < 0.001). This simple system using bleach disinfectant and special storage vessels prevents bacterial contamination of ORS and reduces the risk of nosocomial transmission of cholera and other enteric pathogens. Since its discovery in the mid-1960s, oral rehydration solution (ORS), hailed as "the greatest medical discovery of the 20th century,"[1] has become the cornerstone of modern therapy for cholera and pediatric diarrheal disease and has saved countless lives around the world [2]. Despite evidence that enteropathogenic bacteria survive and multiply in ORS [3-5] and that ORS prepared in the developing world is frequently contaminated with these pathogens [6-10] the benefits of administering ORS to dehydrated patients with diarrhea have always been perceived as outweighing the risks. Storage vessels: Vessel A is the pre-intervention container In many clinics in the developing world, where access to potable water is limited, ORS is prepared from water that has not been chlorinated or boiled. Even in clinics that use safe water, ORS may easily become contaminated when it is stored in open buckets or extracted by patients or staff dipping cups and hands into large open containers (Figure A). A simple system for point-of-use disinfection and safe storage [11] has proven to be highly effective in improving the microbiologic quality of household drinking water [12,13] and of street-vended beverages [14]. We reasoned that the elements of this system (point-of-use water treatment with sodium hypochlorite disinfectantused to dispense oral rehydration solution on the cholera ward. and the use of closed, narrow-mouth storage vessels with spigots) could easily be adapted to preparation and storage of ORS. METHODS Study site and procedures Guinea-Bissau has experienced recurrent epidemic cholera since 1987. During the most recent epidemic from October 6, 1996 through November 15, 1997, more than 25,000 cases of cholera and nearly 1,000 associated deaths were reported. Bissau, the capital city, reported more than 18,000 cases and 225 cholera deaths. Many oral rehydration treatment centers were established in response to the epidemic. In Bissau, approximately 80% of cholera patients seeking treatment were referred to the cholera ward of Simão-Mendes National Hospital. At Simão-Mendes Hospital, ORS was prepared at 8:00 AM every morning in two 10-liter plastic buckets and one 50-liter plastic barrel. Every morning, the clinic staff person responsible for preparing ORS would discard any remaining from the previous day and rinse the buckets and barrel with soap and untreated municipal tap water. After rinsing, the containers were used to prepare 50–70 liters of ORS in 10-liter batches by adding one packet of oral rehydration salts for every liter of tap water. Once the ORS was prepared, two drops of commercial bleach (5% sodium hypochlorite) (Lavax ®; Brandesco Company, Lisbon, Portugal) per liter of ORS was added to the containers. The two full 10-liter buckets were then placed on the cholera ward, where patients could obtain ORS either by dipping their own cup into the bucket or by asking another patient or a nurse to do so. Each patient received a makeshift 8- or 16-ounce cup, often made from an empty intravenous fluid bottle, on admission to the cholera ward. Nursing staff seldom spontaneously offered ORS to patients. When the 10-liter buckets were empty or nearly empty, clinic staff would refill them by either dipping the 10-liter bucket inside the 50-liter ORS storage barrel or by using a cup to scoop ORS out of the 50-liter barrel and into the 10-liter bucket. We conducted an intervention trial to determine whether disinfecting water with bleach before ORS preparation and using closed, narrow-mouth vessels for ORS preparation and storage would improve the microbiologic quality of ORS prepared at Simão Mendes Hospital. Cholera ward intervention During the study period, a patient census on the cholera ward was obtained from the medical staff and clinic log book. Cholera patients were confirmed by collecting rectal swabs for culture from selected patients. Patient and medical staff satisfaction with the intervention was assessed through open-ended interviews during the post-intervention period. For five consecutive days, samples of tap water were collected at 8:00 AM, and samples of ORS were collected from each container at 8:00 AM, 4:00 PM, and 8:00 AM the following morning. We then instructed hospital staff to use four 20-liter, closed, narrow-mouth vessels with spigots for preparing, storing, and dispensing ORS each morning, instead of their usual containers (Figure B).Storage vessels: Vessel B is the plastic container used in the intervention trial. The ORS preparer was instructed to rinse the inside of each vessel thoroughly with 2 drops of the commercial bleach solution in 1 liter of water each morning before making new ORS. Once the rinsed vessels were filled with tap water, the ORS preparer added two drops of bleach per liter of water to each vessel and allowed disinfection to occur for 30 min before adding packaged oral rehydration salts. The vessels were then placed on the wards to be used as needed (Figure B). After a two-day adaptation period, we resumed microbiologic testing according to the previous schedule for five additional days. Follow-up visits for sample collection and testing were