Communicable Disease Surveillance Centre, Temple of Peace and Health, Cathays Park, Cardiff, UK.
J Water Health. 2010 Jun;8(2):299-310. doi: 10.2166/wh.2009.184. Epub 2009 Nov 9.
An outbreak in the autumn of 2005 resulted in 218 confirmed cases of Cryptosporidium hominis. The attack rate (relative risk 4.1, 95%CI 2.8-9.1) was significantly higher in the population supplied by Cwellyn Water Treatment Works (WTW). A case-control study demonstrated a statistically significant association (odds ratio 6.1, 95% CI 1.8-23.8) between drinking unboiled tap water and C. hominis infection. The association remained significant in a logistic regression analysis, with an adjusted odds ratio of 1.30 (95 CI 1.05-1.61) per glass of unboiled tap water consumed per day. This evidence together with environmental and associated microbiological investigations, and the absence of effective treatment to remove Cryptosporidium oocysts at the WTW, led to the conclusion that the outbreak was waterborne. Oocyst counts in final treated water at the WTW and at different points in the distribution system were consistently very low, maximum count in continuous monitoring 0.08 oocysts per 10 litres. Data from continuous monitoring and the epidemic curve is consistent with the hypothesis that low numbers of oocysts of C hominis were present in treated water continuously during the outbreak and these were of sufficient infectivity to cause illness. All surface water derived water supplies present a potential risk to human health and appropriate control measures should be in place to minimise these risks.
2005 年秋的一次爆发导致 218 例确诊的人隐孢子虫病。供水来自 Cwellyn 水净化厂（WTW）的人群发病率（相对风险 4.1，95%CI 2.8-9.1）明显更高。病例对照研究表明，饮用未煮沸的自来水与 C. hominis 感染之间存在统计学显著关联（比值比 6.1，95%CI 1.8-23.8）。在逻辑回归分析中，这种关联仍然显著，每天饮用未煮沸的自来水每增加一杯，调整后的比值比为 1.30（95%CI 1.05-1.61）。这一证据以及环境和相关微生物学调查，以及在 WTW 没有有效的处理方法来去除隐孢子虫卵囊，得出结论认为该爆发是水源性的。WTW 及分配系统不同点的最终处理水中的卵囊计数一直非常低，连续监测中的最大计数为每 10 升 0.08 个卵囊。连续监测和流行曲线的数据与假设一致，即爆发期间处理水中持续存在少量具有足够感染力的人隐孢子虫卵囊，这些卵囊足以引起疾病。所有源自地表水的供水都对人类健康构成潜在风险，应采取适当的控制措施来最大限度地降低这些风险。
