Cyclospora cayetanensis was identified in 176 returned travellers from the Riviera Maya region of Mexico between 1 June and 22 September 2015; 79 in the United Kingdom (UK) and 97 in Canada. UK cases completed a food exposure questionnaire. This increase in reported Cyclospora cases highlights risks of gastrointestinal infections through travelling, limitations in Cyclospora surveillance and the need for improved hygiene in the production of food consumed in holiday resorts.
On 14 July 2015, Health Protection Scotland (HPS) identified an unusual increase in Cyclospora infections in travellers to Mexico. National and international partners were informed and upon further investigation, a total of 176 cases have been identified in England, Scotland, Wales and Canada. An outbreak control team managed the investigation in the United Kingdom (UK). UK patients were interviewed about travel history, food consumption, clinical symptoms and demography using a questionnaire. The majority of cases had travelled to the Riviera Maya region of Mexico.
Investigation of UK cases
Cyclospora cases were identified in primary clinical diagnostic and commercial laboratories by microscopy or molecular testing. Cases were confirmed in reference laboratories using microscopic methods (e.g. examination of a wet preparation by bright field microscopy and, if structures resembling Cyclospora were observed, viewing under UV light for autofluorescence). In addition, smears were permanently stained using modified Ziehl Neelsen and examined.
In the UK, probable cases were defined as individuals with onset of gastrointestinal (GI) symptoms or a specimen date on or after 1 June 2015, travel to Mexico in the previous 14 days and C. cayetanensis oocysts identified in stool specimens by a local diagnostic laboratory. Confirmed UK cases were probable cases confirmed microscopically by national reference laboratories. Cases without either local or national reference laboratory confirmation were excluded from this analysis. No cases associated with travel to Mexico were identified in the UK in 2015 before 1 June.
Outbreak description
Between 1 June and 22 September 2015, 79 probable or confirmed case-patients (hereafter called cases) were reported in England (n = 55), Scotland (n = 21) and Wales (n = 3). No further cases linked to Mexico have been identified in the period since that date (as at 28 October 2015). Symptom onset dates were available for 62 confirmed or probable cases and ranged from 8 June to 19 August 2015 (Figure 1). Travel information was available for 60 cases; the earliest departure date from the UK to Mexico was 22 May and the latest date of return was 30 August 2015. The median age of cases was 44 years (range: 15–66) with 46 of 79 cases 40 years and older; 43 of 79 were female. Only 43 of the 79 cases diagnosed in local laboratories were confirmed by a reference laboratory.
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