Outbreak of disease in Yellowbourne

Microbial indicators are useful tools for identifying faecal contamination. Total and faecal coliforms have been used extensively for many years for the purpose of confirming faecal contamination. However, in recent years, several limitations in the utility of the coliforms as indicators of faecal pollution have been unravelled by scientists leading to additional microbes ( e.g., E. coli, enterococci, and Clostridium perfringens as well as viruses) being suggested for use as alternative indicators (Griffin et al., 2001). The enterococcus group is a subgroup of the faecal streptococci that includes at least five species and enterococci have been used successfully as indicators of faecal pollution (Cabelli et al., 1982). "Indicator organisms are useful in that they circumvent the need to assay for every pathogen that may be present in water. Ideally, indicators are nonpathogenic, rapidly detected, easily enumerated, have survival characteristics that are similar to those of the pathogens of concern, and can be strongly associated with the presence of pathogenic microorganisms" (Scott et al., 2002).
Understanding the origin of faecal pollution is vital both for assessing associated health risks and initiating necessary remedial actions while the problem exists as it is well established that the majority of the contaminating organisms are not limited to humans but also exist in the intestines of many other warm-blooded animals (Orskov and Orskov, 1981). To meet the challenge of identifying sources of faecal pollution, various microbiological methods have been proposed, one of them being the determination of the ratio of faecal coliforms to faecal streptococci. The advantages of using this method are that the assay requires minimal expertise to perform while being able to provide rapid results (Clesceri et al., 1998).
This is a report of the Public Health Investigation into the outbreak of diarrhoea in Yellowbourne during April – May, 1997.
The outbreak of diarrhoea commenced in Yellowbourne on 18 April, 1997 when the first case, a 24 year old male, took ill with symptoms of watery diarrhoea. He was admitted to the local hospital the next day, i.e., on the evening of 19 April, 1997 for rehydration and medical care. Three days later, on 22 April 1997, 3 more patients suffering from watery
diarrhoea received treatment from a G.P. One of the patients, a young child, was severely dehydrated, and the G.P immediately had him admitted to a regional hospital. The number of cases escalated over the next few days and the local Environmental Health department was alerted. In all, 182 people were affected. Common symptoms reported included fever, nausea, loss of appetite as well as watery diarrhoea. The town of Yellowbourne has a population of 157,460.
Data pertaining to the potential source of illness were collected by the Environmental Health department through visits to or telephoning each adult patient. In the case of children under 18 years of age, the information was obtained from their parents.
Faecal samples were collected and sent for analyses of pathogenic organisms at the microbiology department of Yellowbourne hospital. The tests were repeated by specialists at reference laboratories.
The potable water supply system as well as the area of its location were