title: Oyster-associated outbreaks of Norovirus gastroenteritis in Singapore.
abstract: Outbreaks of gastroenteritis associated with the consumption of raw imported half-shelled frozen oysters occurred in Singapore between 16 Dec 2003 and 04 Jan 2004. A total of 305 cases were reported with clinical symptoms of diarrhoea (94%), abdominal cramps (72%), vomiting (69%) and fever (54%). The median incubation period was 30.8h and the duration of illness was 2-3 days. The overall relative risk of oyster consumption was 14.1 (95% CI: 8.3-24.0, P<0.001). Stool and oyster samples tested negative for common bacterial pathogens, including Vibrio parahaemolyticus. However, stool samples were positive for the presence of Norovirus group II RNA via RT PCR while oyster samples indicated the presence of Norovirus particles by electron microscopy. The clinical and epidemiological features were suggestive of Norovirus gastroenteritis and were subsequently confirmed by laboratory tests of stools and implicated oysters. Steps have been taken to ensure that food outlets do not thaw frozen oysters and serve them raw.
authors.affiliation: Communicable Disease Division and Disease Control Branch, Ministry of Health (MOH), 16 College Road, College of Medicine Building, Singapore.
authors.forename: T L
authors.initials: TL
authors.lastname: Ng
authors.forename: P P
authors.initials: PP
authors.lastname: Chan
authors.forename: T H
authors.initials: TH
authors.lastname: Phua
authors.forename: J P
authors.initials: JP
authors.lastname: Loh
authors.forename: R
authors.initials: R
authors.lastname: Yip
authors.forename: C
authors.initials: C
authors.lastname: Wong
authors.forename: C W
authors.initials: CW
authors.lastname: Liaw
authors.forename: B H
authors.initials: BH
authors.lastname: Tan
authors.forename: K T
authors.initials: KT
authors.lastname: Chiew
authors.forename: S B
authors.initials: SB
authors.lastname: Chua
authors.forename: S
authors.initials: S
authors.lastname: Lim
authors.forename: P L
authors.initials: PL
authors.lastname: Ooi
authors.forename: S K
authors.initials: SK
authors.lastname: Chew
authors.forename: K T
authors.initials: KT
authors.lastname: Goh
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D016022:Case-Control Studies; D002648:Child; D004196:Disease Outbreaks; D005260:Female; D005759:Gastroenteritis / Q000453:epidemiology* / Q000821:virology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D029322:Norovirus / Q000302:isolation & purification*; D010125:Ostreidae / Q000821:virology*; D057096:Shellfish Poisoning; D012846:Singapore / Q000453:epidemiology