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Volume 11, Number 2—February 2005

Research

Sporadic Cryptosporidiosis Decline after Membrane Filtration of Public Water Supplies, England, 1996–2002

Stella Goh*, Mark Reacher†Comments to Author , David P. Casemore‡, Neville Q. Verlander§, André Charlett§, Rachel M. Chalmers¶, Margaret Knowles#, Anthony Pennington*, Joy Williams*, Keith Osborn**, and Sarah Richards††
Author affiliations: *Carlisle and District Primary Care Trust, Carlisle, United Kingdom; †Health Protection Agency, Cambridge, United Kingdom; ‡University of Wales, Aberystwyth, Ceredigion, Wales, United Kingdom; §Health Protection Agency Centre for Infections, Colindale, London, United Kingdom; ¶Singleton Hospital, Swansea, Wales, United Kingdom; #Cumberland Infirmary, Carlisle, United Kingdom; **United Utilities, Great Sankey, Warrington, United Kingdom; ††West Cumberland Hospital, Whitehaven, United Kingdom

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Table 2

Baseline characteristics of case-patients and controls

Characteristics n (%)
Before membrane filtration,
March 1, 1996–February 29, 2000 After membrane filtration,
March 1, 2000–August 31, 2002 Before and after membrane filtration,
March 1, 1996–August 31, 2002
Case-patients, total 153 (100) 22 (100) 175 (100)
Sex
Female 70 (45.8) 15 (68.2) 85 (48.6)
Male 83 (54.2) 7 (31.8) 90 (51.4)
Age
<1–5 87 (56.9) 9 (40.9) 96 (54.9)
6–15 47 (30.7) 7 (31.8) 54 (30.9)
16+ 19 (12.4) 6 (27.3) 25 (14.3)
Water sources and water supply zones
Crummock Lake
Crummock North 37 (24.2) 2 (9.1) 39 (22.3)
Crummock South 19 (12.4) 4 (18.2) 23 (13.1)
Ennerdale Lake
Ennerdale North 30 (19.6) 2 (9.1) 32 (18.3)
Ennerdale South 13 (8.5) 1 (4.5) 14 (8.0)
Other sources
Millom 19 (12.4) 3 (13.6) 22 (12.6)
Quarry Hill 16 (10.5) 6 (27.3) 22 (12.6)
Hausegill 3 (2.0) 0 3 (1.7)
Hayknott 2 (1.3) 0 2 (1.1)
Underscar 1 (0.7) 2 (9.1) 3 (1.7)
Fellside 0 0 0
Mixed >1 source 11 (7.2) 1 (4.5) 12 (6.9)
Different private water supplies 2 (1.3) 1 (4.5) 3 (1.7)
Controls, total 468 (100) 69 (100) 537 (100)
Sex
Female 234 (50) 31 (44.9) 265 (49.3)
Male 234 (50) 38 (55.1) 272 (50.7)
Age
<1–5 273 (58.3) 27 (39.1) 300 (55.9)
6–15 137 (29.3) 20 (29.0) 157 (29.2)
16+ 58 (12.4) 12 (17.4) 70 (13.0)
Water sources and water supply zones
Crummock Lake
Crummock North 104 (22.2) 7 (10.1) 111 (20.7)
Crummock South 49 (10.5) 13 (18.8) 62 (11.5)
Ennerdale Lake
Ennerdale North 100 (21.4) 7 (10.1) 107 (19.9)
Ennerdale South 43 (9.2) 3 (4.3) 46 (8.6)
Other sources
Millom 54 (11.5) 10 (14.5) 64 (11.9)
Quarry Hill 42 (9.0) 16 (23.2) 58 (10.8)
Hausegill 5 (1.1) 0 5 (0.9)
Hayknott 6 (1.3) 1 (1.4) 7 (1.3)
Underscar 3 (0.6) 6 (8.7) 8 (1.5)
Bridgend 0 2 (2.9) 2 (0.4)
Fellside 1 (0.2) 0 1 (0.2)
Mixed* 51 (10.9) 4 (5.8) 55 (10.2)
Different private water supplies 10 (2.1) 0 10 (1.9)

*Mixed: mixed supply derived from Ennerdale and Crummock, or from Ennerdale and another source, or from Crummock and another source.

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