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
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.