Following the introduction of an improved surveillance
system for infectious intestinal disease
outbreaks in England and Wales, the Public Health Laboratory Service Communicable
Surveillance Centre received reports of 26 outbreaks between 1 January
1992 and 31 December
1995 in which there was evidence for waterborne transmission of infection.
In these 26
outbreaks, 1756 laboratory confirmed cases were identified of whom 69 (4%) were admitted to
hospital. In 19 outbreaks, illness was associated with the consumption
of drinking water from
public supplies (10 outbreaks) or private supplies (9 outbreaks). The largest
of 575 cases. In 4 of the remaining 7 outbreaks, illness was associated
with exposure to
swimming pool water. Cryptosporidium was identified as the probable causative
all 14 outbreaks associated with public water supplies and swimming pools.
was responsible for most outbreaks associated with private water supplies.
This review confirms
a continuing risk of cryptosporidiosis from chlorinated water supplies
in England and Wales,
and reinforces governmental advice to water utilities that water treatment
processes should be
rigorously applied to ensure effective particle removal. High standards
of surveillance are
important for prompt recognition of outbreaks and institution of control
microbiological evidence of water contamination may be absent or insufficient
to implicate a
particular water supply, a high standard of epidemiological investigation
is recommended in all
outbreaks of suspected waterborne disease.