Outbreak of cryptosporidiosis at a California waterpark: employee and patron roles and the long road towards prevention

Abstract

In August-September 2004, a cryptosporidiosis outbreak affected >250 persons who visited a California waterpark. Employees and patrons of the waterpark were affected, and three employees and 16 patrons admitted to going into recreational water while ill with diarrhoea. The median illness onset date for waterpark employees was 8 days earlier than that for patrons. A case-control study determined that getting water in one's mouth on the waterpark's waterslides was associated with illness (adjusted odds ratio 7.4, 95% confidence interval 1.7-32.2). Laboratory studies identified Cryptosporidium oocysts in sand and backwash from the waterslides' filter, and environmental investigations uncovered inadequate water-quality record keeping and a design flaw in one of the filtration systems. Occurring more than a decade after the first reported outbreaks of cryptosporidiosis in swimming pools, this outbreak demonstrates that messages about healthy swimming practices have not been adopted by pool operators and the public.

Fig. 1

Number of ill patrons (n=244^a) and waterpark employees (n=19^b) by reported date of illness onset, 21 July–13 September 2004. (^a Two patrons not represented on the graph gave their onset dates as 8 and 21 June; ^b one employee not represented on the graph gave an onset date of 4 July.)

Fig. 2

Reported exposure and onset dates by patrons (n=151) who reported visiting Waterpark A only once during the illness incubation period, 2004.