context: Cabool, Mo. (population 2090) is located in the Ozark  hills, near the border with Arkansas.
  Untreated groundwater quality was not a factor  but some disturbances in the distribution system, possibly 43 water meter replacements and 2 line breaks,  may have allowed contaminants to enter the water supply.
  Illness was restricted to people using public water supply.
  An  outbreak of gastrointestinal illness  attributed to E. coli 0157:H7 occurred in a  groundwater supply that had been historically  characterized as being of excellent quality  and not in need of disinfection.
  During  the period 15 December 1989-20 January 1990,  residents and visitors to the community of Cabool,  Mo., experienced 243 cases of diarrhea (85 bloody)  and four deaths (Swerdlow et al., 1992).
  A recent disease outbreak resulting in 4 deaths, 32 hospitalizations and a total of 243  documented cases of diarrhea was linked epidemiologically and by on-site data gathering supported by  the use of a distribution system model to the public water supply.
  During  the period 15 December 1989-20 January 1990,  residents and visitors to the community of Cabool,  Mo., experienced 243 cases of diarrhea (85 bloody)  and four deaths (Swerdlow et al., 1992).
  This time in  a community with an outbreak of 243 cases  of bloody diarrhea and 4 deaths.  
  A recent disease outbreak resulting in 4 deaths, 32 hospitalizations and a total of 243  documented cases of diarrhea was linked epidemiologically and by on-site data gathering supported by  the use of a distribution system model to the public water supply.
  A recent disease outbreak resulting in 4 deaths, 32 hospitalizations and a total of 243  documented cases of diarrhea was linked epidemiologically and by on-site data gathering supported by  the use of a distribution system model to the public water supply.
  During  the period 15 December 1989-20 January 1990,  residents and visitors to the community of Cabool,  Mo., experienced 243 cases of diarrhea (85 bloody)  and four deaths (Swerdlow et al., 1992).
  This time in  a community with an outbreak of 243 cases  of bloody diarrhea and 4 deaths.  
  The pathogenic agent, Escherichia Coli  serotype 0157:H7, was isolated from patients' feces in tests conducted by the Centers for Disease Control
  Escherichia Coli serotype 0157:H7 was found in the  feces of some infected individuals.
  An  outbreak of gastrointestinal illness  attributed to E. coli 0157:H7 occurred in a  groundwater supply that had been historically  characterized as being of excellent quality  and not in need of disinfection.
  This was the second reported waterborne  occurrence of E. Coli 0157:H7.
  This time in  a community with an outbreak of 243 cases  of bloody diarrhea and 4 deaths.  
  An  outbreak of gastrointestinal illness  attributed to E. coli 0157:H7 occurred in a  groundwater supply that had been historically  characterized as being of excellent quality  and not in need of disinfection.
  At the invitation of the CDC (U.S. Public Health  Service), the Missouri State Health Department and  the Missouri Department of Natural Resources,  staff members of the U.S. Environmental Protection  Agency (EPA), Drinking Water Research Division  (Cincinnati, Ohio) went to Cabool to review data,  conduct a sanitary survey and collect additional  water samples to be sent to the EPA Research Center  in Cincinnati for further study.
  In addition, attempts were  made to model the distribution system for movement  of water through the system. 
  A general inspection of  the drinking water supply system and operating  practice was also conducted.
  This investigation provided the first opportunity to use a distribution system model to  study the pattern of illness occurrences in  relation to normal water movement patterns  in the distribution system, develop descriptions in water flow caused by line breaks and  map the diffusion of a pathogenic agent  through either line breaks or meter replacements.
  During  the period 15 December 1989-20 January 1990,  residents and visitors to the community of Cabool,  Mo., experienced 243 cases of diarrhea (85 bloody)  and four deaths (Swerdlow et al., 1992).
  Since this investigation of the water system was conducted 4 weeks after  the main impact of the outbreak had subsided, the  strategy for investigating the possible involvement  of water supply focused on the study of long term  monitoring data from the groundwater supply (aquifer  and distribution quality).
  The Centers  for Disease Control (CDC) conducted a household  survey from which they concluded that persons living  inside the city (on the municipal water) were 18.2  times more likely to develop bloody diarrhea than  for persons living outside the city using private well  water.
  After a boil water order was issued (5 January  1990) in the city of Cabool, the number of new cases  rapidly declined.
  The city authorities implemented a  chlorination program for the community water supply  on 12 January.
  Special water samples of 200 ml volume were collected on 14 and 15 February 1990 from the distribution network in addition to sample collections at the two operating wells  (well Nos 5 and 6) for analyses at the EPA Research Center,  Cincinnati.
  These water samples were analyzed for total coliform bacteria by the membrane filter method using m-Endo LES  agar and m-T7 agar.
  In the Cabool outbreak, elderly persons were  more likely to become ill and the four deaths were  among elderly citizens.
  
answers: {'answer_start': [4908], 'text': ['chlorination program ']}