Published Date: 1999-11-25 23:50:00
Subject: PRO/EDR> Cryptosporidiosis, swimming pools - UK (England)
Archive Number: 19991125.2087
CRYPTOSPORIDIOSIS, SWIMMING POOLS - UK (ENGLAND)
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See Also
Cryptosporidiosis - UK (NW England) 990514201611Cryptosporidiosis - UK 980510215948
Cryptosporidiosis - UK (04) 980520072311
Cryptosporidiosis, human - New Zealand (02) 991018082203
Cryptosporidiosis - Australia (Victoria) (02) 980404084359
Date: Fri, 26 Nov 1999
From: Chan Yow Cheong mailto:chanyowcheong@pacific.net.sg
ProMED-mail Regional Moderator for Asia
Source: Eurosurveillance Weekly, 26 Nov 1999 [Edited}
<http://www.eurosurv.org/update/>
Four recent outbreaks of cryptosporidiosis associated with swimming pools
in England have drawn attention to transmission of infection in this
setting and the difficulty of investigating prolonged outbreaks that may be
associated with a continuing source of low level contamination. These
episodes highlight the continuing challenge of ensuring that swimming pool
treatment systems control protozoan infections.
Fifty-one cases of cryptosporidiosis have been identified in the county of
Oxfordshire in the past 12 weeks compared with 12 expected. Thirty of the
cases live in the Oxford City district (one of five districts in the
county). Interviews with 17 of the 30 implicated recent use of a local
swimming pool and a case control study is in progress to test the
association. Review of the pool's operation revealed that the level of
chlorination had been increased in the two months before the outbreak to
compensate for faulty ozonisation of the water. Routine water samples
contained high counts of coliforms and _Escherichia coli_. The pool was
closed and expert advice on the water treatment system was sought. Oocysts
of cryptosporidium were detected in water from the strainer basket,
flocculation gel, and filter core sand of the swimming pool. Enhanced
surveillance for cases has continued. The water treatment regimen has been
modified, the ozonator has been brought back into service, and the pool has
reopened.
An outbreak in the county of Leicestershire that appears to be linked to
swimming in a particular pool has been identified through the detection of
higher than normal rates of cryptosporidiosis over a period of six weeks.
Interviews with patients revealed that 14 had used the pool before they
became ill. This pool also used ozonation. It was closed and expert advice
on the water treatment system was sought. Cysts of giardia but not
cryptosporidia were detected in the main pool water and from scrapings from
the pool sieve and filter sand. Core sand has not yet been examined.
An increased number of cases of cryptosporidiosis have been reported in
south west London since September. Initial investigations indicated various
potential contributory risk factors but 10 cases have now been linked to a
swimming pool at a leisure centre. Samples of pool water have been
negative; further investigations are underway.
Sixteen cases of cryptosporidiosis were detected in Solihull in the West
Midlands between late August and mid October and all were associated with a
single swimming pool. Cryptosporidial oocysts were identified in samples of
water from the adult (9/10L) and learner pools (188/10L). The pool was
closed. Filters were backwashed and cleaned repeatedly until counts were
zero. No further cases have been identified since the pool reopened.
The increase in ascertainment of outbreaks probably reflects increased
local scrutiny of cryptosporidium. Some small outbreaks associated with
swimming pools are probably not reported nationally. As many swimming pool
outbreaks have been reported in the past two years as in the previous six
years. Outbreaks of infection associated with swimming pools are being
reviewed.
Please send details of any outbreaks in the past ten years in your European
country to Mark Reacher (mreacher@phls.nhs.uk) or Gordon Nichols
(gnichols@phls.nhs.uk) at the PHLS Communicable Disease Surveillance Centre
(tel: +44 (0)20 8200 6868; fax: +44 (0)20 8200 7868).
Reported by Gordon Nichols (gnichols@phls.nhs.uk), Environmental
Surveillance Unit, PHLS Communicable Disease Surveillance Centre, London,
England.
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