title: Norovirus outbreak associated with undercooked oysters and secondary household transmission.
abstract: During December 2009, over 200 individuals reported gastrointestinal symptoms after dining at a North Carolina restaurant. An outbreak investigation included a case-control study of restaurant patrons, a secondary household transmission study, environmental assessment of the restaurant facilities and operations, and laboratory analysis of stool and food samples. Illness was primarily associated with consumption of steamed oysters (odds ratio 12, 95% confidence interval 4·8-28) and 20% (8/41 households) reported secondary cases, with a secondary attack rate of 14% among the 70 susceptible household contacts. Norovirus RNA was detected in 3/5 stool specimens from ill patrons; sequencing of RT-PCR products from two of these specimens identified identical genogroup II genotype 12 sequences. Final cooked temperatures of the steamed oysters were generally inadequate to inactivate norovirus, ranging from 21°C to 74°C. Undercooked contaminated oysters pose a similar risk for norovirus illness as raw oysters and household contacts are at risk for secondary infection.
authors.affiliation: Wake County Human Services, Raleigh, NC 27610, USA. Edie.AlfanoSobsey@wakegov.com
authors.forename: E
authors.initials: E
authors.lastname: Alfano-Sobsey
authors.forename: D
authors.initials: D
authors.lastname: Sweat
authors.forename: A
authors.initials: A
authors.lastname: Hall
authors.forename: F
authors.initials: F
authors.lastname: Breedlove
authors.forename: R
authors.initials: R
authors.lastname: Rodriguez
authors.forename: S
authors.initials: S
authors.lastname: Greene
authors.forename: A
authors.initials: A
authors.lastname: Pierce
authors.forename: M
authors.initials: M
authors.lastname: Sobsey
authors.forename: M
authors.initials: M
authors.lastname: Davies
authors.forename: S L
authors.initials: SL
authors.lastname: Ledford
mesh_terms: D000328:Adult; D000818:Animals; D017250:Caliciviridae Infections / Q000453:epidemiology* / Q000635:transmission / Q000821:virology; D016022:Case-Control Studies; D002648:Child; D003296:Cooking; D004196:Disease Outbreaks; D005243:Feces / Q000821:virology; D005260:Female; D005759:Gastroenteritis / Q000453:epidemiology* / Q000821:virology; D006801:Humans; D008297:Male; D029322:Norovirus / Q000302:isolation & purification*; D009657:North Carolina / Q000453:epidemiology; D010125:Ostreidae / Q000821:virology*; D012367:RNA, Viral / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017423:Sequence Analysis, RNA; D012758:Shellfish / Q000821:virology*
chemical_list: D012367:RNA, Viral