A community outbreak of food-borne small round-structured virus gastroenteritis caused by a contaminated water supply

In August 1994, 30 of 135 (23 %) bakery plant employees and over 100 people from South Wales and Bristol in the United Kingdom, were affected by an ou tbreak of gastroenteritis. Epidemiological studies of employees and three c ommunity clusters found illness in employees to be associated with drinking cold water at the bakery (relative risk 3.3, 95%, CI 1.6-7.0), and in comm unity cases with eating custard slices (relative risk 19.8, 95%, CI 2.9-135 .1) from a variety of stores supplied by one particular bakery. Small round -structured viruses (SRSV) were identified in stool specimens from 4 employ ees and 7 community cases. Analysis of the polymerase and capsid regions of the SRSV genome by reverse transcription-polymerase chain reaction (RT-PCR ) demonstrated viruses of both genogroups (1 and 2) each with several diffe rent nucleotide sequences. The heterogeneity of the viruses identified in t he outbreak suggests that dried custard mix may have been inadvertently rec onstituted with contaminated water. The incident shows how secondary food c ontamination can cause wide-scale community gastroenteritis outbreaks, and demonstrates the ability of molecular techniques to support classical epide miological methods in outbreak investigations.