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A review of interventions triggered by hepatitis A infected food-handlers in Canada Tricco, Andrea C; Pham, Ba'; Duval, Bernard; Serres, Gaston D; Gilca, Vladimir; Vrbova, Linda; Anonychuk, Andrea; Krahn, Murray; Moher, David Dec 8, 2006

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ralssBioMed CentBMC Health Services ResearchOpen AcceResearch articleA review of interventions triggered by hepatitis A infected food-handlers in CanadaAndrea C Tricco*†1,2,3, Ba' Pham†1,2,4, Bernard Duval5, Gaston De Serres5, Vladimir Gilca5, Linda Vrbova6, Andrea Anonychuk1,7, Murray Krahn4,7 and David Moher2Address: 1Epidemiology and Biostatistics, GlaxoSmithKline Canada, Mississauga, Ontario, Canada, 2Chalmers Research Group, Children's Hospital of Eastern Ontario Research Institute, Ottawa, Ontario, Canada, 3Institute of Population Health, Ottawa, Ontario, Canada, 4Department of Health Policy, Management and Evaluation, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada, 5Centre de Recherche du CHUQ, Universite Laval, Institut national de santé publique du Québec, Canada, 6University of British Columbia, Department of Health Care and Epidemiology, Vancouver, British Columbia, Canada and 7Division of Clinical Decision Making, Toronto General Research Institute, University Health Network, Toronto, Ontario, CanadaEmail: Andrea C Tricco* - atricco@cheo.on.ca; Ba' Pham - ba.z.pham@gsk.com; Bernard Duval - bernard.duval@ssss.gouv.qc.ca; Gaston De Serres - gaston.deserres@ssss.gouv.qc.ca; Vladimir Gilca - vladimir.gilca@ssss.gouv.qc.ca; Linda Vrbova - vrboval@interchange.ubc.ca; Andrea Anonychuk - andrea.anonychuk@rogers.ca; Murray Krahn - murray.krahn@uhn.on.ca; David Moher - dmoher@uottawa.ca* Corresponding author    †Equal contributorsAbstractBackground: In countries with low hepatitis A (HA) endemicity, infected food handlers are the source of mostreported foodborne outbreaks. In Canada, accessible data repositories of infected food handler incidents are notavailable. We undertook a systematic review of such incidents to evaluate the extent of viral transmission throughfood contamination and the scope of post-exposure prophylaxis (PEP) interventions.Methods: A systematic search of MEDLINE and EMBASE was conducted to identify published reports of incidentsin Canada. An expanded search of a news repository (i.e., transcripts from newspapers and newscasts) was alsoconducted to identify the location and timing of an incident, which was used to retrieve the related report bycontacting local public health departments. Data pertaining to case identification, public health risk, PEPinterventions, and associated costs was independently abstracted by two reviewers and summarized according toincidents with and without large PEP interventions.Results: A total of 16 incidents were identified from 1998–2004. There were approximately 3 incidents requiringpublic notification per year. Only 12.5% of incidents were described in published reports, indicating that publisheddata significantly underestimated the number of incidents and PEP interventions. Data pertaining to the remainingincidents was unpublished, sparse and highly dispersed at the local public health level.Six of the 16 incidents required large PEP interventions to immunize on average 5000 potentially exposedindividuals. Secondary transmission was low. Characteristics of incidents requiring large PEP interventions includedpotentially infectious food handlers working with uncooked food for a prolonged duration in high-volume grocerystores in high-density urban areas.Conclusion: Infected food handlers with hepatitis A virus (HAV) requiring public notification are not infrequentin Canada. Published data severely underestimated the burden of PEP intervention. Better and consistent reportingat the local and national level as well as a national data repository should be considered for the management ofPublished: 08 December 2006BMC Health Services Research 2006, 6:157 doi:10.1186/1472-6963-6-157Received: 10 August 2006Accepted: 08 December 2006This article is available from: http://www.biomedcentral.com/1472-6963/6/157© 2006 Tricco et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Page 1 of 7(page number not for citation purposes)future incidents.BMC Health Services Research 2006, 6:157 http://www.biomedcentral.com/1472-6963/6/157BackgroundIn developed countries, foodborne or waterborne hepati-tis A (HA) outbreaks are relatively uncommon [1]. How-ever, infected food handlers remain the source of mostreported foodborne outbreaks [2]. In many low endemic-ity countries, the potential for food contamination froman infected food handler is a recognized public healthconcern [3]. In these countries, a large proportion of thepopulation has never been exposed or vaccinated againsthepatitis A virus (HAV) and is thus susceptible to infec-tion during potential outbreaks [4]. In Canada, aninfected produce worker in a grocery store triggered a post-exposure prophylaxis (PEP) vaccination campaign of over19,000 potentially exposed residents, causing substantialdisruption to an urban community [5].There are currently no data repositories for incidentsinvolving infected food handlers, although an early detec-tion system for foodborne outbreaks is in place in Canada[6]. Laboratory-confirmed cases infected with HAV arenotifiable on a provincial/territorial and national level,but reporting of follow-up investigations are not manda-tory beyond local public health units. Consequently, dataare not consolidated and often kept in diverse locations[7]. Further encumbering this issue is the fact that only asmall proportion of HAV cases are notified. According toUSA data, only 1 in 10 cases are reported via disease noti-fication systems [8]. We undertook a systematic review ofinfected food handler incidents to evaluate the extent ofviral transmission through food contamination and thescope of PEP interventions.MethodsA literature search of MEDLINE (1966; year of inceptionto March 2005) and EMBASE (1980; year of inception toMarch 2005) was conducted (keywords "hepatitis" and"Canada") to identify published reports of infected foodhandler incidents in Canada. All searches were conductedusing the OVID interface. An expanded search (keywords"hepatitis' AND "food" AND "Canada") of a news reposi-tory (FPinfoMart and Newscan; transcripts from over 200national, provincial and local newspapers and newscastsources: 2000 – the year of establishment – to March2005) was also conducted to identify the location andtiming of an incident. This information was used toretrieve the related unpublished report by contacting thelocal public health department [9,10]. Archives for theCanada Diseases Weekly Report (CDWR; 1975 – Dec.1991, the last year of reporting) and Canada Communica-ble Disease Report (CCDR; 1992 – Mar. 2005) were alsoconsulted [11].A report was included if it described the incident of antences), full-text news articles (i.e., newspaper and news-cast articles), and full-text published reports werereviewed independently by two reviewers. Disagreementswere resolved through discussion.Using the Centers for Disease Control and Preventionframework for the investigation of infectious disease out-breaks [12,13], data pertaining to case identification, pub-lic health risk, PEP interventions, and associated costs wasindependently abstracted by two reviewers. Data wassummarized according to the extent of post-exposure pro-phylactic intervention by the local public health in deal-ing with an infected food handler. Incidents with limitedPEP interventions were those that required 1) a publicnotification to advise the public and healthcare providersto watch out for potential HAV-related symptoms, and/or2) immunization of close contacts (e.g., family, colleaguesat work). In contrast, incidents with large PEP interven-tions were those that required 1) a public notification thatincluded eligibility criteria for vaccination and 2) publicimmunization campaigns.ResultsLiterature searchBetween 1998 and 2004, the systematic review identified16 incidents of infected food handlers in Canada in total(Table 1). Only two of these (12.5%) were described inpublished communicable disease reports and identifiedthrough MEDLINE (Figure 1) [14,15].The expanded search identified the location and timing of15 incidents [5,14-28], one of which was also identifiedthrough the MEDLINE search [15]. This search was sensi-tive to incidents requiring public notification. Subse-quently, 3 public health reports and 12 publicnotifications were obtained (Figure 1, Table 1).Case identificationIn Canada, approximately 3 incidents of infected foodhandlers requiring public notification occurred per yearbetween 2001 and 2004 (Table 1). There were no second-ary cases reported in 12 of the 16 infected food handlercases, most possibly due to timely intervention, highhygiene standards or non-reporting. Most cases were lab-oratory confirmed (Table 2). Cause of infection was iden-tified in 3 of the 16 incidents, including infectionpotentially related to high risk sexual activities [14], con-tact with visitors from high-endemic countries [15], andfood contamination from another infected food handler[17].The two incidents identified through MEDLINE weredescribed in CCDR reports [14,15]. In the first report, aPage 2 of 7(page number not for citation purposes)infected food handler in a food establishment in Canada.Citations, news clips (e.g., titles and the first few sen-link analysis found a 6-week gap between case confirma-tion and public health notification. Several symptomaticBMC Health Services Research 2006, 6:157 http://www.biomedcentral.com/1472-6963/6/157HAV cases, all linked to the restaurant where the indexcase worked, were hospitalized and laboratory-confirmedat the local hospital. Despite these test results, it was a res-taurant employee that notified the local public health unitafter noticing jaundice symptoms among these cases [14].In the second report, prompt reporting and quick follow-up of a case from a deli led to the largest immunoglobulincampaign found in this systematic review (n = 5400; Table1) [15].Evidence of public health riskThe 16 incidents occurred in 8 restaurants, 4 grocerystores, 2 hospital food services and 2 food markets (Table2). Limited PEP interventions were conducted in 7 of the8 incidents in restaurants. Large PEP interventions wereconducted in 3 of the 4 incidents in grocery stores. Inci-dents requiring a large PEP intervention were associatedwith 1) the potential for contamination of uncookedfood, 2) case notification within 14 days of symptomonset (e.g., within an acceptable window for PEP inter-vention), 3) prolonged duration of public exposure priorto notification, and 4) relatively large number of poten-tially exposed clients due to high-volume stores located inhigh-density urban areas [5,17,20]. The median durationof exposure was 18.5 days and 8 days for incidents withrepeated exposure was balanced by high hygiene practiceand the existence of standard procedures for infectiousdisease control [26,28].Post-Exposure Prophylactic interventionsLarge PEP interventions typically included communicabledisease investigation [5,14,15,20], food inspection andcontrol [5,17], risk communication (e.g., news confer-ence, media releases, media interviews, hot-lines and web-sites [5,20]), immunization clinics [5,15,17,19,20,23],and surveillance of secondary cases [5]. The mediannumber of immunized individuals was 5,750 (range 550– 19,208) in incidents with large PEP intervention (Table2). In the majority of incidents, risk communicationincluded details regarding eligibility criteria for immuni-zation and a qualitative statement regarding the potentialrisk to the public (Table 2). Food inspection and controlwas only performed in a few of incidents with limited PEPintervention, yet most of these required risk communica-tion to the public (Table 2).Public health costData regarding resource utilization and direct cost to pub-lic health was limited, except in the incident with the larg-est PEP intervention [5]. The total direct cost to publicTable 1: Identified incidents of HA infected food handlers with confirmed public health reports (n = 16, 1998–2004)Timing of discoveryCity, province Index case, location Total # cases* Public health Intervention# immunized Search method‡, reference #Sep 2004 Okanagan, BC bar worker, restaurant 1 vaccine NR expanded, [27]Apr 2004 Port Clements, BC vegetable department worker, food market1 vaccine NR expanded, [26]Apr 2004 Burlington, ON food service worker, hospital cafeteria 1 doctor referral† NA expanded, [25]Dec 2003 Burlington, ON food service worker, restaurant 1 doctor referral† NA expanded, [24]Jul 2003 Grand Prairie, AB part-time employee, restaurant 1 IG >550 expanded, [23]Apr 2003 Whistler, BC food service worker, 2 restaurants 1 doctor referral† NA expanded, [22]Apr 2003 Winnipeg, MB cases were linked to a restaurant 17 doctor referral† NA expanded, [21]Sep 2002 London, ON food handler in produce department, grocery store1 vaccine 16,320 expanded, [20]Sep 2002 Edmonton, AB food handler, ethnic specialty food market1 IG 2,300 expanded, [19]Aug 2002 Toronto, ON food handler in produce department, grocery store3 vaccine & IG 19,208 expanded, [5]Mar 2002 Vancouver, BC food service worker, 3 grocery stores 8 vaccine & IG 6,100 expanded, [17]Apr 2002 Vancouver, BC server, restaurant 1 doctor referral† NA expanded, [28]Mar 2002 Edmonton, AB worker, lounge 1 IG 50 expanded, [18]Apr 2001 Victoria, BC food handler, hospital food services 1 vaccine NR expanded, [16]Jan 2001 Edmonton, AB deli worker, grocery store 1 IG 5,400 MEDLINE & expanded [15]Nov 1998 Montérégie, QB owner and chef, restaurant 7 IG NR MEDLINE [14]Abbreviations: HA hepatitis A, AB Alberta, BC British Columbia, ON Ontario, QB Quebec, MB Manitoba, NR not reported, NA not applicable, IG administration of hepatitis A immune serum globulin, PEP post-exposure prophylaxis.Notes: *Reported cases only. †Public health asked individuals who displayed any symptoms of hepatitis A to get tested through a family physician. ‡Search method refers to Medline/EMBASE search or the expanded search (i.e., searching news repository for timing and location, which was then verified by the respective public health report).Page 3 of 7(page number not for citation purposes)large and limited PEP intervention, respectively. In twoincidents involving hospital food facilities, the risk ofhealth was $35 per person immunized in a PEP campaignof approximately 19,000 potentially exposed individuals.BMC Health Services Research 2006, 6:157 http://www.biomedcentral.com/1472-6963/6/157This included an average CND $20 for the cost of vaccineand $15.17 for vaccine administration (i.e., in lieu of vac-cine clinics, inspections, and the hotline).DiscussionThis systematic review has a number of limitations. Theliterature search could only identify incidents with a pub-lic health notification. These incidents were evaluated torepresent an infection risk to those who consumed foodprepared by HAV infected food handlers and represent asmall and selective sample of all reported incidents ofinfected food handlers [2]. In other studies, approxi-mately 8% of reported HAV cases involve infected foodinfection risk to those who ate food they had prepared[2,12]. Furthermore, the data we collected was sparse;only one out of every four identified incidents was ade-quately reported. Finally, although the expanded searchwas based upon a news repository of a large number ofdata sources, it has only been offering comprehensive cov-erage since 2000 [9].Despite these limitations, some major findings could bederived from the consolidated data. Highly publicizedinfected food handlers were not infrequent in Canada.Only two of the 16 incidents were described in publishedcommunicable disease reports, indicating that publishedTable 2: Public health investigation of infected food handlers (n = 16, 1998–2004)Items Large PEP intervention (n = 6) Limited PEP intervention (n = 10)Case identificationCase confirmation and cause of infectionLaboratory confirmed case 6 7Known cause of infection 2 1DutiesFood/drink worker in restaurant/lounge 1 7Food handler in produce/deli section, grocery/food store 4 0Food worker in hospital food services/cafeteria 0 2Food/veggie worker in food market 1 1Hygiene practiceHigh standard/met requirements for food handling 4 6Evidence of public health riskTiming of discoveryWithin 14 days of symptom onset 5 4> 14 days of symptom onset 0 6Estimated duration of public exposure in days*Median (range) [# cases with data] 18.5 (4, 23) [n = 6] 8 (3, 45) [n = 9]Qualitative estimate of the number of exposed individualsEstimated number in hundreds or thousands 5 1Unspecified number of clients over an exposed duration 1 9Post-exposure prophylaxis interventionImmunizationVaccine (or vaccine and immunoglobulin) 3 2Immunoglobulin 3 4Doctor referral 0 4Number of immunized individuals† 5750 (550, 19208) [n = 6] All contacts [n = 2], 50 [n = 1]Food safety inspection and controlRecall, remove & clean up potentially contaminated food 3 1Risk communicationEligibility criteria for vaccination 6 8Communicate estimated risk to the public 6 9Public health costReported resources utilization and/or direct cost 5 2Abbreviations: PEP: post-exposure prophylaxis.Notes: *Estimated duration of exposure as specified in eligibility criteria for immunization, or number of days working while potentially infectious. †Median (range) [# cases with data] for large public health interventions and category (i.e., IG all contacts, IG 50 close contacts) [# cases with data] for limited public health interventions.Page 4 of 7(page number not for citation purposes)handlers, approximately 60% of those continue workingwhile potentially infectious, but only 7% represent andata severely underestimated the number of incidents andPEP interventions. These two were probably publishedBMC Health Services Research 2006, 6:157 http://www.biomedcentral.com/1472-6963/6/157due to their atypical nature, as described above. Data per-taining to the remaining incidents was unpublished,sparse and highly dispersed at the local public healthlevel. From a public health perspective, HAV outbreaksand HAV interventions triggered by infected food han-dlers should be reported and shared nationally, perhapsthrough the CCDR. Relying on published data only willresult in an under-estimation of the burden of publichealth interventions.Large PEP interventions to immunize on average 5000potentially exposed clients were required in six of the 16incidents. Secondary transmission was low, although thiscould be due to under-reporting, timely intervention orhigh hygiene standards. Characteristics of incidentsrequiring large PEP interventions included potentiallyinfectious food handlers working with uncooked food fora relatively prolonged duration in high-volume grocerystores located in high-density urban areas. Evaluating sus-pected cases, assessing the need for PEP intervention andimplementing necessary control measures are commonand time-consuming tasks for public health departments[2]. Factors associated with large PEP interventions identi-fied through this research can facilitate the evaluation asto whether such intervention is merited.In Canada, there are currently no data repositories forHAV outbreaks or PEP interventions triggered by HAVinfected food handlers. Laboratory-confirmed casesinfected with HAV are notifiable on a provincial/territo-rial and national level, but reporting of follow-up investi-gations are not mandatory beyond local public healthunits. Only four of the 16 incidents identified were docu-mented with sufficient detail at the local public healthlevel. In one instance, the lack of communication seemedto contribute to secondary cases that were otherwise pre-ventable [14]. Increased surveillance, better communica-tion and data sharing would contribute towards bettermanagement of future cases. Members of our group arecurrently conducting a broad and detailed survey ofinfected food handlers in Canada.Reliable data on infected food handlers is required toaccurately evaluate the burden of PEP interventions. Forexample, 4,000 more people were vaccinated in the inci-dent with the largest PEP intervention identified here [5]than the total number of 15,000 vaccinees during one ofthe largest HAV outbreaks in Canada between 1995 and1997 [29]. In fact, PEP intervention triggered by a singleinfected food handler could be more costly to publichealth than the control of a peak outbreak in recent years.It has been suggested that the cost associated with themanagement of infected food handlers should beprograms. Currently, these management costs are notcommonly accounted for in such analyses [30].A previous cost effectiveness analysis suggested that vacci-nating food service workers in states with elevated HAVrates prior to routine childhood vaccination was cost-effective [31]. However, a simulation study concludedthat vaccinating restaurant employees was unlikely to beeconomical from either the restaurant owner or the soci-etal perspective, even during HAV epidemics [32]. Ourresults showed that limited PEP interventions were suffi-cient to contain potential transmission from infected foodworkers in restaurants. Large PEP interventions might,however, become necessary in infected cases working inhigh-volume food establishments in high-density urbanareas.Countries such as Canada with low HA endemicity haveexperienced declining incidence of new cases of HAV inthe past decade [33]. However, this has led to a decreasedprevalence of antibody to HA in the population, resultingin an adult population not protected against HAV [33]. Inthe meantime, sporadic outbreaks of foodborne HA,related and unrelated to a food handler, continue to occur[2,33-35]. Recently, contaminated green onions wereserved to customers of a single restaurant in Pennsylvania,leading to a large outbreak in the United States [34].HAV-infected food handlers have been the source of mostreported foodborne HA outbreaks. Six outbreaks thatoccurred in the 1990s have recently been document in areview of HA foodborne transmission [2]. Our results areconsistent with observations elsewhere; a single infectedfood handler can transmit HAV to dozens or even hun-dreds of individuals and cause substantial economic bur-den [2,30]. Specific public health interventions [34,36,37]are required to contain this form of transmission untilhigh levels of immunity are achieved across all age groups,perhaps as a result of routine HA vaccination [33,35].Universal immunization of young children, implementedin some western and south-western parts of the UnitedStates, substantially reduced the incidence of HAV [38].Due to its cost-effectiveness potential, this policy is beingconsidered for other regions [39,40], including calls for itsexpansion nationally [41]. In Canada, the current immu-nization strategy to control HA is to vaccinate groups atrisk [42]. However, this strategy has been shown as inef-fective among travelers [43] and very limited data areavailable on its effectiveness in other risk groups. Recentseroprevalence studies indicate that only 3% of childrenages 8–13 are protected against HAV [44], whereas diseaseacquisition occurs in adulthood with approximately 10%Page 5 of 7(page number not for citation purposes)accounted for in cost-effectiveness evaluations of control of Canadians infected by ages 24–29 [11,45-47]. Concernwith this seemingly lack of protection has led to calls forBMC Health Services Research 2006, 6:157 http://www.biomedcentral.com/1472-6963/6/157the reassessment of the current policy regarding HA vacci-nation [4,44,48]. Universal vaccination could eliminatethe spectrum of PEP interventions related to HA cases infood handlers that emerge periodically [33].The importance of foodborne viral infections is increas-ingly recognized [2,3]. Food handlers can transmit infec-tion during preparation or serving; fruit and vegetablesmay be contaminated by fecally contaminated water usedfor growing and washing. The globalization of the foodindustry and the ease of cross-border shipment of freshand frozen food means that a contaminated food itemmay not be limited to one location. To meaningfullymonitor increases or decreases in foodborne diseaserequires an effective surveillance system at the local andnational levels. This should include standardized report-ing of foodborne incidents and a national repository forconsolidated data on these incidents.ConclusionInfected food handlers with HAV requiring public notifi-cation are not infrequent in Canada. Published dataseverely underestimated the burden of PEP intervention.Better and consistent reporting at the local and nationallevel as well as a national data repository should be con-sidered for the management of future incidents.Competing interestsFunding for this systematic review was provided by Glax-oSmithKline Canada. ACT has held various research con-tracts with the R&D department of GlaxoSmithKline,Canada. BP is employed by GlaxoSmithKline, Canada. AAhas held various research contracts with the R&D depart-ment of GlaxoSmithKline, Canada. BD, GDS, and VGhave received research funding from the R&D departmentof GlaxoSmithKline, Canada. LV, MK, and DM declarethat they have no competing interests.Authors' contributionsACT contributed to the development of the research ques-tion and methodology, conducted the literature searches,article screening, data abstraction, project management,and interpretation of the results. BP contributed to thedevelopment of the research question and methodology,article screening, data abstraction, project management,and interpretation of the results. BD, GDS and VG con-tributed to the development of the research question andmethodology, provided data from a survey of infectedfood handlers reported to Quebec public health units(data not shown but used in the interpretation of the cur-rent results), provided guidance on obtaining publichealth reports, and interpretation of the results. LV con-tributed to the development of the methodology, pro-the follow-up national survey. AA contributed to dataabstraction, project management, and interpretation ofthe results. MK contributed to the development of theresearch question and methodology, obtained publichealth reports, and interpretations of the results. DM con-Study flowFigure 1Study flow. Notes: *This number is an approximation due to the commercial coverage of media sources by the news repository. †Reason for exclusion of news clips and news articles were not categorized, as only the location and timing data were used. Reports from MEDLINE & EMBASE n=2  Reports from Expanded Search n=15 Already found in MEDLINE/EMBASE search n=1 ___________________________________________ Total Identified Reports n=16 Citations from Medline & EMBASE search n=413 ___________________________________________ News clips from the news repository search n=347* Full-text articles retrieved n=66  Full-text news articles retrieved n=274† Citations excluded n=347 Reasons: HBV n=95; HCV n=64; HDV n=3; HEV n=6; HGV n=2; HBV/HCV n=18; Animal study n=14; Commentary n=24; Other n=121 ___________________________________________ News clips excluded n=73† Articles excluded n=47 Reasons: HAV articles: Review n=9, Guides n=5,  Not an infected food handler case n=17;  Other viral hepatitis n = 16   News articles excluded n=187† Confirmed Reports n=14 Found by contacting PH department directly n=8 Found by searching PH websites n=4 Could not be found n=2 Page 6 of 7(page number not for citation purposes)vided guidance on obtaining public health reports,interpretation of the results, and is currently conductingtributed to the development of the research question andmethodology, provided guidance on handling of grey lit-BMC Health Services Research 2006, 6:157 http://www.biomedcentral.com/1472-6963/6/157erature in a systematic review, and interpretation of theresults. All of us contributed to the manuscript writingand approved the final version of the manuscript.AcknowledgementsThis study was funded by GlaxoSmithKline, Canada. The funding body had no role in study design; in the collection, analysis, and interpretation of data; in the writing of the manuscript; and in the decision to submit the manu-script for publication.The authors would like to thank Perica Sever and Reid Robson for all of their support on this research. We would also like to thank Richard Foty, Brenda Lee, and Leanne De Souza for their assistance with this project.References1. Acheson DW, Fiore AE: Preventing foodborne disease--whatclinicians can do.  N Engl J Med 2004, 350:437-440.2. Fiore AE: Hepatitis A transmitted by food.  Clin Infect Dis 2004,38:705-715.3. Koopmans M, Vennema H, Heersma H, van SE, van DY, Brown D,Reacher M, Lopman B: Early identification of common-sourcefoodborne virus outbreaks in Europe.  Emerg Infect Dis 2003,9:1136-1142.4. 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