Volume 11, Number 2—February 2005
Research
Sporadic Cryptosporidiosis Decline after Membrane Filtration of Public Water Supplies, England, 1996–2002
Stella Goh*, Mark Reacher†
, David P. Casemore‡, Neville Q. Verlander§, André Charlett§, Rachel M. Chalmers¶, Margaret Knowles#, Anthony Pennington*, Joy Williams*, Keith Osborn**, and Sarah Richards††
, David P. Casemore‡, Neville Q. Verlander§, André Charlett§, Rachel M. Chalmers¶, Margaret Knowles#, Anthony Pennington*, Joy Williams*, Keith Osborn**, and Sarah Richards††
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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