title: Epidemiology of foodborne norovirus outbreaks in Catalonia, Spain.
abstract: BACKGROUND
  Noroviruses are one of the principal biological agents associated with the consumption of contaminated food. The objective of this study was to analyse the size and epidemiological characteristics of foodborne outbreaks of gastroenteritis in Catalonia, a region in the northeast of Spain.
  
  
  METHODS
  In all reported outbreaks of gastroenteritis associated with food consumption, faecal samples of persons affected were analysed for bacteria and viruses and selectively for parasites. Study variables included the setting, the number of people exposed, age, sex, clinical signs and hospital admissions. The study was carried out from October 2004 to October 2005.
  
  
  RESULTS
  Of the 181 outbreaks reported during the study period, 72 were caused by Salmonella and 30 by norovirus (NoV); the incidence rates were 14.5 and 9.9 per 100,000 person-years, respectively. In 50% of the NoV outbreaks and 27% of the bacterial outbreaks (p = 0.03) the number of persons affected was > or =10; 66.7% of NoV outbreaks occurred in restaurants; no differences in the attack rates were observed according to the etiology. Hospitalizations were more common (p = 0.03) in bacterial outbreaks (8.6%) than in NoV outbreaks (0.15%). Secondary cases accounted for 4% of cases in NoV outbreaks compared with 0.3% of cases in bacterial outbreaks (p < 0.001)
  
  
  CONCLUSIONS
  Norovirus outbreaks were larger but less frequent than bacterial outbreaks, suggesting that underreporting is greater for NoV outbreaks. Food handlers should receive training on the transmission of infections in diverse situations. Very strict control measures on handwashing and environmental disinfection should be adopted in closed or partially-closed institutions.
authors.affiliation: Department of Health, Autonomous Government of Catalonia, Barcelona, Spain. a.martinez@gencat.cat
authors.forename: Ana
authors.initials: A
authors.lastname: Martinez
authors.forename: Angela
authors.initials: A
authors.lastname: Dominguez
authors.forename: Nuria
authors.initials: N
authors.lastname: Torner
authors.forename: Laura
authors.initials: L
authors.lastname: Ruiz
authors.forename: Neus
authors.initials: N
authors.lastname: Camps
authors.forename: Irene
authors.initials: I
authors.lastname: Barrabeig
authors.forename: Cesar
authors.initials: C
authors.lastname: Arias
authors.forename: Josep
authors.initials: J
authors.lastname: Alvarez
authors.forename: Pere
authors.initials: P
authors.lastname: Godoy
authors.forename: Pilar Jorgina
authors.initials: PJ
authors.lastname: Balaña
authors.forename: Analia
authors.initials: A
authors.lastname: Pumares
authors.forename: Rosa
authors.initials: R
authors.lastname: Bartolome
authors.forename: Dolors
authors.initials: D
authors.lastname: Ferrer
authors.forename: Unai
authors.initials: U
authors.lastname: Perez
authors.forename: Rosa
authors.initials: R
authors.lastname: Pinto
authors.forename: Javier
authors.initials: J
authors.lastname: Buesa
mesh_terms: D001424:Bacterial Infections / Q000453:epidemiology / Q000382:microbiology; D017250:Caliciviridae Infections / Q000453:epidemiology*; D004196:Disease Outbreaks; D005243:Feces / Q000382:microbiology; D005506:Food Contamination; D005517:Foodborne Diseases / Q000453:epidemiology* / Q000382:microbiology; D005759:Gastroenteritis / Q000453:epidemiology* / Q000382:microbiology; D006801:Humans; D015994:Incidence; D029322:Norovirus / Q000302:isolation & purification*; D011446:Prospective Studies; D012147:Restaurants; D012307:Risk Factors; D013030:Spain