The detection of cryptosporidium oocysts in three of the four pools at Pool Complex A supported the findings of the case-control study. It is transmitted mainly by ingestion of water or food contaminated with oocysts excreted in animal or human faeces. The infective dose of C. parvum has been shown to be as low as 30 oocysts and may even be lower. The main clinical symptom is diarrhoea, which may be profuse and watery, often accompanied by abdominal pain, fever, malaise and vomiting. The illness usually lasts between 1 and 3 weeks, and while it is generally self-limiting, may be prolonged or even fatal in immunocompromised individuals.
Available treatment is limited to providing relief of symptoms.
During these months there were 104 reports compared with 37 notifications for January and February in 1997. A case was defined as any person residing in the Redland Shire or the southern suburbs of Brisbane City who had an illness characterised by diarrhoea, vomiting or abdominal pain and had laboratory-confirmed Cryptosporidium oocysts detected in their stools during this period. Persons diagnosed before this period were not interviewed because of the potential for poor recall. Secondary household cases were excluded from the case-control study. Controls were excluded if they had a history of enteric illness in the preceding 2 weeks.