Select Committee on Health Appendices to the Minutes of Evidence

Attachment 6



  Improvements in mains water treatment over the last 50 years have virtually eliminated outbreaks of bacterial and viral infection that prior to then had caused substantial morbidity and mortality. However, outbreaks of infection with cryptosporidium (a small protozoal organism) associated with mains water still occur, as do bacterial and viral outbreaks associated with private water supplies (many of which do not have adequate treatment). In addition, many sporadic infections within the community are probably related to drinking water consumption. Recent large outbreaks of waterborne infection with significant mortality in the USA and Canada have been potent reminders of what can happen if infection control measures fail.

  There are a small number of cryptosporidium outbreaks associated with water every year, causing much significant diarrhoeal disease. The Government has introduced legislation through the Department of the Environment, Transport and the Regions (DETR) to monitor cryptosporidium contamination in drinking water supplies that are thought to be at risk of cryptosporidium contamination. The national data on cryptosporidium monitoring is likely to provide information on the extent of water contamination, and an opportunity to compare water contamination with disease prevalence. There is also a need to look at waterborne disease associated with private water supplies. Key to this comparison between clinical and water data is the collection of post code information on both, and the application of geographic information systems (GIS) to the analysis of these data.


  The large recent outbreak of E.coli O157 in Walkerton, Canada affecting over 2,000 people from a population of 5,000 highlights the importance of maintaining drinking water of good microbiological quality, especially in rural and private supplies. The DETR regulations have been introduced to ensure that public supplies are protected from contamination. The danger in not acting is that clear evidence of the effectiveness of the cryptosporidium regulations will not be identified, and the risks of E.coli O157 outbreaks associated with private supplies will remain.


  The Public Health Laboratory Service interacts with the Department of Health, the Drinking Water Inspectorate, the Environment Agency, the Association of Port Health Authorities and the UK Water Industry in work to ensure that drinking water is safe. During waterborne outbreaks there is interaction, through the outbreak control team, with Consultants in Communicable Disease Control, geologists, water engineers and individual water companies.


  The conversion of current surveillance systems to improve the geographic analysis of water and health requires the collection of post-coded data and its analysis within a GIS system. The tightening of data confidentiality requirements following the Caldicott report makes the development of such a geographic surveillance system more demanding, as the key to such systems is use of the full post code. It is likely that IT solutions to the problem within the Communicable Disease Surveillance Centre are possible, but further funding is required.


  The PHLS role is best achieved through development of a GIS capability as its Communicable Disease Surveillance Centre and adoption of specific enhanced surveillance projects to compare water quality in public and private supplies with the occurrence of human diseases. There should be a medium term aim to promote the routine reporting of post code with other surveillance reporting. The GIS capacity would also enhance surveillance for other infections of public health importance.


  The confidence of the public with its water supply is crucially dependent on the continued co-ordinated efforts of many agencies to ensure that it is safe to drink.

  Prepared by Drs Gordon Nichols, Sarah O'Brien and Professor Paul Hunter. Public Health Laboratory Service.

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Prepared 28 March 2001