Background: An outbreak of gastroenteritis was investigated following complaints of illness after eating donuts from a food premises in the Australian Capital Territory (ACT).
Methods: Food poisoning complainants and contacts were surveyed using a standard gastroenteritis questionnaire including menu items from the food premises. Descriptive analyses were performed on data collected for all responses. A case-control study was conducted for a group of 140 people at a catered function. Food safety inspections were conducted with food and environmental samples tested at the ACT Government Analytical Laboratory. Stool specimens were collected from cases who were ill at the time of interview. Neither active case finding, nor viral testing of food or environmental samples, could be conducted.
Results: Three hundred and one people were surveyed, and 215 individuals (71.4%) reported vomiting and/or diarrhoea following consumption of a donut purchased from the business over a five-day period. All ill respondents reported eating a donut. The medians of incubation period and illness duration were 34 hours (interquartile range, IQR: 29-42 hours) and 48 hours (IQR: 29-72 hours) respectively. Diarrhoea, vomiting and abdominal pain were the most commonly reported symptoms. Eight out of 11 specimens collected from ill individuals were positive for norovirus. For the case-control study, data from 59 attendees were collected, with an attack rate of 46% (27/59). Eating any kind of filled donut was associated with a person becoming ill (odds ratio: 10.4; 95% confidence interval: 1.18-478.13). No single flavour was identified as the likely source of infection. Elevated levels of coliforms were present in two samples of donut filling obtained during the food safety inspection.
Conclusion: Donuts are a novel vehicle for norovirus infection. This implicated pathogen, plus evidence collected at the food premises suggestive of faecal contamination, indicates the source of this outbreak was likely an ill food handler. The findings of this outbreak highlight the importance of excluding food handlers from work while ill. While this was one of the largest foodborne outbreaks investigated in the ACT, the true extent of illness remains unknown. Active case finding should be pursued to determine the magnitude of outbreaks.
Keywords: case-control study; donuts; food handling; foodborne disease; gastroenteritis; norovirus; outbreak.
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