acute infectious gastrointestinal illnesses in humans are usually mild diseases , although 
 they can be severe , even fatal , or lead to long - term sequelae . they occur frequently and 
 thus represent a significant burden for society [ 14 ] . their aetiology includes viruses , 
 bacteria and parasites that are transmitted primarily through the faecal  oral route . many of 
 these diseases are zoonotic in origin , from a wide range of reservoirs including livestock , 
 pets , and wildlife ( mammals , birds , reptiles ) . as a result , their epidemiology is complex , 
 with people being exposed in numerous circumstances and through several transmission routes 
 ( foodborne , waterborne , contact with animals and their environment , contact with sick people 
 or shedders ) . epidemiological case - control studies have highlighted potential risk factors associated 
 with increased risk of disease . these risk factors can be specific ( one food type ) , 
 especially when searching for the source of an outbreak , or quite broad ( representing a 
 pathway of exposure ) . for example , two recent outbreak investigations of salmonellosis 
 linked 33 cases in canada and 272 cases in the usa to the consumption of head cheese   and imported black and red pepper , respectively . moreover , a population - based research 
 study conducted in 2004 in the usa on 1316 campylobacteriosis cases identified a spectrum of 
 risk factors , including owning a pet puppy , 
 drinking untreated water , and eating chicken prepared at a restaurant , etc . . outside of case - control investigations , the exposure of individuals to a variety of risks 
 ( foods , behaviours , environments ) is rarely measured . however , this exposure information is 
 essential for microbial exposure assessments , either qualitative or quantitative , for 
 attribution analyses [ 7 , 9 , 10 ] , and ultimately to rank 
 risks and prioritize prevention and control measures . exposure assessment models are based on the proportion of people in the population that are 
 exposed ( occurrence ) and the number of times they are exposed ( frequency ) over a given 
 period of time , combined with the dose ( i.e. the concentration of the pathogen in the 
 source ) . in the case of campylobacter infections , for example , exposure 
 assessment has also been used to perform attribution . in this study , exposure has been described for various commodities and routes 
 of transmission for a given pathogen and then ranked to most effectively target prevention 
 and control measures . in other studies , the exposure assessment is targeted to one food 
 commodity and forms a component of a larger quantitative risk assessment model , estimating 
 the number of human cases attributable to the considered commodity or route of transmission 
 [ 1214 ] . the more precise the distributions of exposure to pathogens are measured , the narrower the 
 output of the risk modelling and the clearer the interpretation and decisions based on this 
 output . in canada , there is a lack of exposure information for the general or healthy population 
 that could be used to develop these types of exposure assessments for various enteric 
 diseases . this study was designed to measure the occurrence of exposures ( associated with 
 enteric pathogen risks previously documented ) in a sample of healthy individuals , i.e. 
 people that did not have vomiting or diarrhoea in the past 314 days , in a canadian 
 community corresponding to a c - enternet ( canada 's integrated enteric disease surveillance 
 system ) sentinel site . the objective of the study was to consider different recall periods 
 to reflect different disease incubation windows , to investigate the impact of 
 population - related characteristics ( age , gender ) and disease - related characteristics 
 ( seasonality and incubation period ) on the exposure frequencies . the study was based on a cross - sectional telephone survey on known exposures for common 
 gastrointestinal illnesses . each month , about 100 respondents were enrolled over a 
 12-month period ( august 2009 to july 2010 ) , to account for expected seasonality in some 
 exposures . respondents were randomly assigned to one of three recall periods ( 3 days , 7 
 days , 14 days ) , to cover the range of incubation periods of gastrointestinal diseases 
 caused by viruses , bacteria and parasites , and were asked about their exposures in the 
 past 3 , 7 or 14 days . the study population was the region of waterloo ( row ) , ontario , canada . this area is a 
 sentinel site for the canadian integrated enteric pathogen surveillance programme 
 ( c - enternet ) where all reportable gastrointestinal disease cases are comprehensively 
 followed - up by the local public health authority for potential exposures . it is comprised 
 of three cities ( cambridge , kitchener , waterloo ) and four townships ( north dumfries , 
 wellesley , wilmot , woolwich ) . in 2010 , the estimated population was 527031 residents 
 ( population and household estimates , regional municipality of waterloo , october 2011 ) . the survey was approved by the public health agency of canada research ethics board 
 ( reb-2008 - 0040 ) and the university of waterloo office of research ethics ( ore no . the sampling frame was based on a geographically stratified , general phone population 
 random sampling program purchased from asde survey sampler . households were selected from 
 the list of telephone numbers through multi - stage random sampling and then the individual 
 in the household with the next birthday was selected to perform the interview ( provided 
 they were eligible and consented ) . participants were selected proportional to the 
 population and age distributions in row based on age - specific population estimates for 
 2006 ( rowph , 2007 ) . individuals were eligible for inclusion if they resided at a residence with a listed 
 telephone number in row , spoke english and did not have diarrhoea or vomiting in the 
 recall period prior to the interview . trained interviewers conducted calls monday to 
 friday from 09:00 to 21:00 hours . up to three attempts on different days and at different 
 times of the day were made to reach each household selected and up to five attempts were 
 made to contact the specific individual selected from the household . interviews of 
 children aged < 18 years required parental agreement ; the respondent could be a 
 proxy or the child itself . the survey questionnaire was adapted from the enhanced sporadic enteric disease case 
 questionnaire that had been previously developed and used for the systematic follow - up of 
 reported cases of gastrointestinal illness in row ( http://www.phac-aspc.gc.ca/c-enternet/publications-eng.php ) . the survey included questions on demographics ( age , gender , occupation ) and questions to 
 measure the frequency of exposure to potential sources of enteric pathogens including 
 water ( drinking and recreational water ) , food supply ( type of shop for usual food and meat 
 purchases , origin of the food coming from outside the home ) , high - risk foods 
 ( unpasteurized products , spoiled and undercooked food ) , environment ( country property , 
 animals , gardening , outdoor activities ) , travel , and social events ( barbecuing , social 
 gathering ) . the same questions were asked for each recall period group . the age of respondents was divided 
 into six age groups : 0<5 , 5<15 , 15<30 , 30<45 , 
 45<60 , 60 years old . interview months were categorized into seasons : winter 
 ( december  february ) , spring ( march  may ) , summer ( june  august ) and autumn 
 ( september  november ) . occupation was categorized into agriculture / food processing , food 
 preparation , daycare service , healthcare service and other , to distinguish high - risk 
 occupational exposures . the animals that people were exposed to when living on or visiting 
 a farm , a country property or a petting zoo were extracted from the text question and 
 categorized into cattle , cat , dog , rodent , rabbit , poultry , other poultry ( i.e. not 
 chicken ) , horse , sheep , reptile , pig , llama and other . some variables were merged based on 
 similar exposure routes : recreational water ( dichotomized into natural waters 
 vs. pool ) , the consumption of all unpasteurized products ( i.e. milk , milk 
 products , juices , other ) , exposures to all food animals when living on or visiting a farm , 
 country property or petting zoo , and contact with all pets other than cats and dogs . age , gender and season were tested for their homogeneous distribution across the three 
 recall periods , as heterogeneity will impede direct comparisons of results between recall 
 periods . age and gender distribution in the respondents were compared to their distribution 
 in row using a  test of homogeneity . the age and gender 
 structure in each population was further explored by considering the sex ratio for each 
 age group in each population . as fewer than 01% of the responses were unsure ( n  =  102 ) or  refused 
 ( n  =  1 ) , the  refused and yes answers . for each recall period , the 
 proportion of each exposure was computed , as well as its 95% confidence interval . to 
 generate more precise proportions , respondents from two or three recall periods were 
 pooled whenever possible , if the confidence intervals for each recall period overlapped 
 for a given exposure . the proportion of each exposure and its confidence interval was 
 computed again after appropriate pooling of recall periods . exposure proportions for the row population were 
 extrapolated from the pooled proportions by direct standardization for age and gender . the influence of age , gender , and season on the pooled exposure proportions was tested 
 using a logistic regression model with a two - step approach : for each exposure , univariable 
 models were assessed to test for age , gender and season independently and the variables 
 for which p  <  01 in the univariable models were tested in a 
 multivariable model without interaction . this process was conducted for exposures with a 
 proportion 10% in at least one of the recall periods . the similarities and ordinal ranking of the proportions observed across the three recall 
 periods were used to provide a sense of the exposure periodicity , which we defined as the 
 interval of time ( days ) between two consecutive instances of the same exposure . based on 
 logic and considering that we had no information on how many times the exposure occurred 
 during the recall period , we estimated that , for example , when the occurrence of an 
 exposure is stable from the 3- to the 7-day recall period , then the probability for it to 
 happen at least once is the same in both periods so that its periodicity is 3 days . if 
 the occurrence significantly increases from the 3- to the 7-day recall period , then the 
 probability for it to happen at least once is higher in the 7-day period , so that its 
 periodicity is > 3 days . thus , when the exposure proportion increased significantly 
 from the 3- to the 7-day and again to the 14-day recall period , the exposure period was 
 considered to be > 7 days . when the exposure proportion for the 7- and 14-day recall 
 periods were equal and greater than that of the 3-day recall period , the exposure period 
 was considered to be between 4 and 7 days . when all exposure proportions were equal , the 
 exposure period was considered as <3 days . multiple correspondence analysis ( mca )   was 
 performed on the 14-day recall period data , to explore the existence of unique exposure 
 profiles in healthy people . four independent mcas were run independently : the first on 
 permanent exposures , including place of residence ( i.e. living on a farm or in a country 
 property ) , source of drinking water and use of in - home water treatment ; the second , on 
 place of residence , and common ( i.e. not during a visit ) exposure to farm animals and 
 household pets ; the third on point exposures through occasional activities or behaviours 
 ( i.e. drinking raw water , swimming in a pool , swimming in other recreational water , 
 canoeing or hiking , gardening , attending a barbecue , attending a social event , consumption 
 of undercooked food , consumption of unpasteurized food , visiting a farm or country 
 property , contact with farm animals during a visit , and international travel ) ; and the 
 fourth on variables that describe places where food was acquired ( i.e. place of general 
 food shopping , place of meat shopping , and origin of food prepared outside the home ) . age , 
 gender and season were included in the last two analyses to assess the effects of age , 
 gender or season on those exposures . a sample size of 1200 respondents was achieved , with an overall response rate of 462% . fifty - one persons were excluded because of gastrointestinal syndromes ( corresponding to an 
 estimated prevalence of 2% ) . the average number of call attempts made to reach the 
 respondents was 14 , ranging from one to four call attempts . the interview length ranged 
 from 5 to 24  min with a mean duration of 8  min . the interviews were not uniformly spread across the 12-month study period due to an 
 interviewer error that occurred from september to november . the compromised interviews 
 ( n  =  52 ) were discarded and additional interviews were conducted during 
 the last 2 months to achieve the sample size . the number of interviews per weekday was 
 greater on wednesdays ( 27% of all respondents ) and lower on fridays ( 14% ) . thirty - one 
 interviewed respondents aged < 15 years completed the interview on their own , rather 
 than using an adult proxy . they were excluded from the analysis due to concern about 
 reliability of their answers . a total number of 1169 questionnaires were used : 405 for the 
 3-day recall period , 378 for the 7-day recall period , and 386 for the 14-day recall period . the distribution of respondents by age , 
 gender , and season was homogeneous across the three recall periods 
 (  homogeneity tests : p values > 005 ) . compared to the study population , the sampled population had relatively more females ( 624% 
 vs. 501% ) , more people aged > 44 years ( 453% vs. 
 357% ) and fewer people aged between 15 and 44 years ( 368% vs. 455% , 
 fig . thus , it was necessary to standardize the 
 results for age and gender , when inferring to the row population . 1.relative age distribution among the sampled population ( by recall period ) and among 
 the study population ( the region of waterloo , 492000 inhabitants in 2006 ) . relative age distribution among the sampled population ( by recall period ) and among 
 the study population ( the region of waterloo , 492000 inhabitants in 2006 ) . table 1 summarizes the distribution of 
 respondents to 46 potential exposures for each recall period . the proportions of most 
 exposures were similar across the recall period groups ( n  =  35 ) , thus their 
 periodicity was estimated to be <3 days . eight exposures had an estimated periodicity 
 between 3 and 7 days ( the 7- and 14-day recall period proportions were higher ) , and three 
 exposures ( shopping at farmers ' market , purchasing leafy greens , consuming food from 
 fast - food chain restaurant ) had an estimated periodicity > 7 days ( significant 
 increase from the 3- to the 7-day recall periods and from the 7- to the 14-day recall 
 periods ) . the standardized exposure proportions for row show that the most common exposures 
 are municipal water and bottled water as drinking sources ( 718% and 570% , respectively ) , 
 the exposure to households pets in general ( 659% ) and especially dogs ( 497% ) and cats 
 ( 359% ) , and eating food prepared outside the home ( 780% ) , especially from fast - food chain 
 restaurants ( 566% ) and eat - in restaurants ( 510% ) . table 1.observed proportion and 95% confidence intervals of various exposures by recall 
 period in 1169 healthy individuals sampled in the region of waterloo ( row ) , ontario , 
 august 2009july 2010 , and estimates for the sampled and study populationsproportion in the 3-day recall period 
 ( r3 ) ( n  =  405)proportion in the 7-day recall period 
 ( r7 ) ( n  =  378)proportion in the 14-day recall period 
 ( r14 ) ( n  =  386)estimated exposure period ( days)*pooled recall periodproportion based on pooled recall period 
 ( sampled population)age- and gender - standardized proportion 
 to row ( study population)%(95% ci)%(95% ci)%(95% ci)%(95% ci)%(95% ci ) 
 waterborne routes of exposure 
 drinking water source : private well52(3278)90(63123)67(4497)p  <  3r3+r7+r1469(5585)70(5486 )  drinking water source : municipal water691(644736)746(699789)702(654747)p  < 3r3+r7+r14713(686738)718(666770 )  drinking water source : bottled water553(503602)534(483586)598(548648)p  <  3r3+r7+r14562(533591)570(524616 )  drinking water source : other27(1448)40(2265)44(2670)p  <  3r3+r7+r1437(2749)34(2345 )  use in home treatment462(412512)487(435538)484(434536)p  < 3r3+r7+r1430(2141)32(2144 )  swim in or go into a pool91(65124)159(123200)197(158240)p  <  3r3+r7+r14148(128170)154(130178 )  swim or go into water other than pool81(57113)108(79144)135(102173)p  <  3r3+r7+r14108(91127)117(95139 ) 
 environmental exposures 
 go canoeing , hiking35(1957)48(2874)78(53109)p  <  3r3+r7+r1453(4167)56(4171 )  live on a farm or country property54(3481)66(4396)60(3888)p  <  3r3+r7+r1460(4775)59(4573 )  live with contact with food animals25(1245)29(1551)16(0634)p  < property67(4496)116(86153)137(105176)p  <  3r3+r7+r14106(89125)109(88129 )  visit farm or country property and contact with food 3r3+r7+r14127(108147)133(111155 )  gardening215(176258)286(241334)301(255349)p  <  3r3+r7+r14266(241292)261(230292 ) 
 social events 
 attend a barbecue220(18026.3)341(294391)378(330429)3<p  <  7r3+r7+r14311(285339)333(297370 )  attend social gathering156(122195)320(273370)376(327426)3<p  <  7r7+r14348(314383)353(308398 ) 
 travel 
 travel outside canada17(0735)21(0941)34(1857)p  <  3r3+r7+r1424(1634)24(1434 ) 
 food purchasing / consumption behaviours 
 shop for food in supermarket825(784860)966(942982)969(946984)3<p  <  7r7+r14967(952979)966(8921000 )  shop for food at farmers ' market77(53107)196(157239)301(255349 ) 
 p  >  7 
 r14301(255349)296(239354 )  shop for food in butcher 's shop54(3481)148(114188)210(170254)3<p  <  7r7+r14179(153208)183(151216 )  shop for food in farm laneway , farm stand25(1245)53(3381)101(73136)p  < 3r3+r7+r1459(4674)60(4575 )  shop for food from other location47(2872)32(1755)44(2670)p  <  3r3+r7+r1441(3054)39(2751 ) 
 meat purchasing behaviours 
 eat meat purchased from another place than grocery 
 store200(16224 . 3r3+r7+r1423(1533)30(1843 )  consume meat from butcher126(95162)188(150231)192(154235)p  <  3r3+r7+r14168(147190)177(150203 )  consume meat from kill52(3278)69(4599)70(47100)p  <  3r3+r7+r1463(5079)69(5286 )  consume meat from other source64(4293)74(50105)109(80144)p  <  3r3+r7+r1482(6799)87(68105 ) 
 leafy green purchasing 
 purchase leafy greens516(466566)754(707797)847(807882 ) 
 p  >  7 
 r14847(807882)845(747942 ) 
 food outside home 
 eat food prepared outside the home575(526624)741(693784)785(741825)3<p  < 7r7+r14763(731793)780(713847 )  food from fast food chain restaurant316(271364)421(370472)531(480582 ) 
 p  >  7 
 r14531(480582)566(482649 )  food from eat - in restaurant264(222310)452(401504)544(493595)3<p  < <  3r3+r7+r1448(3662)49(3563 )  consume unpasteurized products ( dairy , juice , milk , 
 etc.)62(4090)93(65126)145(111184)p  <  3r3+r7+r1499(83118)107(87128 ) 
 high - risk occupations 
 agriculture sector occupation07(0221)13(0431)05(0119)r3+r7+r1409(0416 )  food preparation occupation20(0939)26(1348)10(0326)r3+r7+r1419(1228 )  daycare occupation02(0014)08(0223)08(0223)r3+r7+r1406(0212 )  healthcare occupation30(1551)21(0941)26(1247)r3+r7+r1426(1736)*p , exposure period , based on the overlapping of proportion confidence intervals 
 between the recall periods and defined by the interval of time ( days ) between two 
 consecutive exposures of the same kind ( <3 days if the exposure proportions 
 are equal across all recall periods , 47 days if the proportions are equal across 
 the 7- and 14-day recall periods and greater than in the 3-day recall period , over 7 
 days if the proportions increased with the length of the recall period).exposure periods between 3 and 4 days are highlighted in grey , and exposure periods 
 > 7 days are in bold font.r3 , 3-day recall period ; r7 , 7-day recall period ; r14 , 14-day recall period . observed proportion and 95% confidence intervals of various exposures by recall 
 period in 1169 healthy individuals sampled in the region of waterloo ( row ) , ontario , 
 august 2009july 2010 , and estimates for the sampled and study populations p , exposure period , based on the overlapping of proportion confidence intervals 
 between the recall periods and defined by the interval of time ( days ) between two 
 consecutive exposures of the same kind ( <3 days if the exposure proportions 
 are equal across all recall periods , 47 days if the proportions are equal across 
 the 7- and 14-day recall periods and greater than in the 3-day recall period , over 7 
 days if the proportions increased with the length of the recall period ) . exposure periods between 3 and 4 days are highlighted in grey , and exposure periods 
 > 7 days are in bold font . r3 , 3-day recall period ; r7 , 7-day recall period ; r14 , 14-day recall period . the effect of age , gender and/or season was statistically significant for 32 exposures 
 ( table 2 ) . age was significant for 23 exposures , 
 season for 18 , and gender for three exposures . simultaneous effects of age , gender and 
 season were significant for those who reported attending a barbecue . table 2.age , gender and season effects on exposures in healthy individuals sampled in the 
 region of waterloo , ontario , august 2009-july 2011age ( years)genderseason0<55<1515<3030<4545<60>60 
 male 
 femalespringsummer 
 autumn 
 winterdrinking water source : municipal water720%734% 
 747% 
 652%*drinking water source : bottled water419%*615%671%*538% 
 590% 
 442%***526%647% * * 
 519% 
 532%drinking water source : other34%20% 
 21% 
 72%*use in home water treatment435%561%**550%**471% 
 430% 
 433%swim in or go into a pool387%***264%***158%**159% * * 
 82% 
 76%72%315% * * * 
 114% 55%*go canoeing , hiking , camping51%92% * 
 38% 
 20%swim or go into waters other than pool ( lake , river)97%155%*108%163% * 
 95% 
 45%*89%199% * * * 
 72% 
 48%visit a farm or country property161%81%108%159% * 
 92% 
 76%75%***116% * 
 177% 
 68%***contact with food animals102%109%*68%89% * 
 31% 
 20%21%***69% 
 130% 
 30%**contact with households pets661%723%698%625% * 
 715% 
 509%***contact with pet = cat610%449%*548%585% 
 587% 
 456%*pets other than cats and dogs98%280%**335%***223% * 
 124% 
 53%*gardening226%230%158%***293% 
 295% 
 344%280%454% * * * 
 274% 
 24%***attend a barbecue306%345%293%423% * 
 302% 
 219% * 
 352% 
 287%**341%*509% * * * 
 241% 
 106%***attend social gathering408%337%459%**333% 
 295% 306%298%*366% 
 429% 
 312%*shop for food in supermarket959%957%926%*985% 
 979% 
 986%shop for food in farmers market222%**409% 
 432% 
 146%***shop for food in butcher shop184%141%196%200% 
 212% 
 122%*shop for food in farm laneway , farm stand34%**75% 
 97% 
 34%**shop for food from other locationeat meat purchased from location other than grocery 
 store323%264%248%274% 
 285% 
 134% * * * 
 286% 
 222%*eat meat from hunting 
 135% 
 62%*eat meat purchased from butcher750%538%*691%667% 
 747% 
 633%60.0%708% 
 600% 
 791%*eat food prepared outside the home633%837%818%837% 
 751% 
 653%*eat food from fast food chain restaurant500%870%*776%698% 
 667% 
 417%**eat food from eat - in restaurant484%*584%612%655% 
 710% 
 729%eat food from eat - in cafeteria29%99%211%**127% 
 101% 
 99%eat food from deli91%62% * 
 127% 
 93%eat food from food vendor71%**149% 
 194% 
 79%**eat undercooked food102%109%203%200% 140% 
 34%**eat any unpasteurized product ( milk , juice , dairy)145%115%135%*111% 
 72% 
 67%72%*90% 
 127% 
 116%bold font indicates the reference category.grey cells indicate non - statistically significant effect.*005<p <  001 , * * 
 001<p  <  0001 , * * * 
 0001<p . age , gender and season effects on exposures in healthy individuals sampled in the 
 region of waterloo , ontario , august 2009-july 2011 bold font indicates the reference category . grey cells indicate non - statistically significant effect . 005<p <  001 , * * 
 001<p some exposures were associated with the summer season , such as consuming bottled water and 
 taking part in outdoor activities ( swimming , canoeing , gardening , barbecuing ) . others were 
 more common in the summer and autumn : having rural contact ( visiting a farm or country 
 property , contact with food animals , acquiring food from farmers ' markets or farm stands ) , 
 attending social gatherings , eating at food vendors or at a delicatessen and consuming 
 unpasteurized products . purchasing meat from a butcher swimming in a pool decreased with age , whereas swimming in natural waters was most common 
 among pre - teen children ( 5 to < 15 years ) and adults aged 3044 years , and this was 
 similar with the reported contact with food animals . extreme ages ( children aged < 5 
 years and adults aged > 60 years ) were less exposed to bottled water and food prepared 
 outside the home . children aged 5 to < 15 years were preferentially exposed to 
 fast - food chain restaurants , and young adults ( 15 to < 30 years ) , to unpasteurized 
 products . respondents aged > 60 years were less frequently exposed to pets and 
 respondents aged 5 to < 30 years were more frequently exposed to non - traditional pets 
 ( neither cats nor dogs ) . finally , gardening was an activity that was more common in people 
 aged > 30 years , barbecuing peaked in respondents aged 30 to < 45 years and 
 social gatherings were most common in respondents aged 15 to < 30 years . men more frequently reported consuming meat from somewhere other than a grocery store , 
 consuming meat from a private hunt and barbecuing . the exploratory description by mca of long - term exposures revealed expected associations . a 
 private well as the main source of drinking water was associated with those who reported 
 living on a farm or a country property and drinking bottled water was associated with those 
 who reported not having water treatment at home ( fig . 
 2 ) . living in the country was associated with exposure to food animals but not to 
 exposure to pets . several point exposures were strongly associated with summer and were less 
 common in the oldest age group ( 60 years ) , such as swimming ( pools and natural waters ) , 
 canoeing or hiking , gardening , barbecuing , visiting a farm , a petting zoo or a country 
 property , and international travel ( fig . 2.map generated through the mca of place of residence , source of drinking water and use 
 of in - home water treatment based on 386 healthy individuals responding to their 
 exposure over the last 14 days . place of residence was living or not in farm or 
 country property ( rural vs. urban ) ; the source of drinking water was 
 a combination of well , municipal , bottled or other water ; and the in - home water 
 treatment was present or absent ( water treatment vs. no water 
 treatment ) . the size of the bubble is proportional to the number of respondents that 
 fall into the category represented by the bubble . bolded text indicates categories contributing to 
 the first axis and underlined text indicates categories contributing to the second 
 axis . number in brackets in the axis title is the axis inertia , which is for 
 categorical variables equivalent to variance for continuous variables . note that 
 several variable categories overlapped near the origin of the axes and are not 
 labelled . 3.map generated through the mca of specific occasional activities or behaviours with 
 age and season based on 386 healthy individuals responding to their exposure over the 
 last 14 days . the occasional activities or behaviours included : drinking raw water 
 ( raw water vs. treated water ) , swimming in a pool ( pool+ vs. - ) , 
 swimming in other recreational water than pool ( other 
 recreational_water  +  vs. - ) , canoeing or hiking ( canoe+ 
 vs. canoe- ) , gardening ( gardening+ vs. - ) , attending 
 a barbecue ( bbq+ vs. - ) , consumption of undercooked food 
 ( undercooked+ vs. - ) , consumption of unpasteurized food 
 ( unpasteurized+ vs. - ) , visiting a farm , a petting zoo , a fair or a 
 country property ( visit+ vs. - ) , contact with food animals during 
 such visit ( food animal contact+ vs. - ) , and international travel 
 ( travel+ vs. - ) ; the age groups were : 04 , 514 , 1529 , 3044 , 4559 , 
 60 years ; the seasons were spring , summer , autumn , winter . the size of the bubble is 
 proportional to the number of respondents that fall into the category represented by 
 the bubble . bolded text indicates categories contributing to the first axis and underlined text 
 indicates categories contributing to the second axis . number in brackets in the axis 
 title is the axis inertia , which is for categorical variables equivalent to variance 
 for continuous variables . note that several variable categories overlapped near the 
 origin of the axes and are not labelled . map generated through the mca of place of residence , source of drinking water and use 
 of in - home water treatment based on 386 healthy individuals responding to their 
 exposure over the last 14 days . place of residence was living or not in farm or 
 country property ( rural vs. urban ) ; the source of drinking water was 
 a combination of well , municipal , bottled or other water ; and the in - home water 
 treatment was present or absent ( water treatment vs. no water 
 treatment ) . the size of the bubble is proportional to the number of respondents that 
 fall into the category represented by the bubble . bolded text indicates categories contributing to 
 the first axis and underlined text indicates categories contributing to the second 
 axis . number in brackets in the axis title is the axis inertia , which is for 
 categorical variables equivalent to variance for continuous variables . note that 
 several variable categories overlapped near the origin of the axes and are not 
 labelled . map generated through the mca of specific occasional activities or behaviours with 
 age and season based on 386 healthy individuals responding to their exposure over the 
 last 14 days . the occasional activities or behaviours included : drinking raw water 
 ( raw water vs. treated water ) , swimming in a pool ( pool+ vs. - ) , 
 swimming in other recreational water than pool ( other 
 recreational_water  +  vs. - ) , canoeing or hiking ( canoe+ 
 vs. canoe- ) , gardening ( gardening+ vs. - ) , attending 
 a barbecue ( bbq+ vs. - ) , consumption of undercooked food 
 ( undercooked+ vs. - ) , consumption of unpasteurized food 
 ( unpasteurized+ vs. - ) , visiting a farm , a petting zoo , a fair or a 
 country property ( visit+ vs. - ) , contact with food animals during 
 such visit ( food animal contact+ vs. - ) , and international travel 
 ( travel+ vs. - ) ; the age groups were : 04 , 514 , 1529 , 3044 , 4559 , 
 60 years ; the seasons were spring , summer , autumn , winter . the size of the bubble is 
 proportional to the number of respondents that fall into the category represented by 
 the bubble . bolded text indicates categories contributing to the first axis and underlined text 
 indicates categories contributing to the second axis . number in brackets in the axis 
 title is the axis inertia , which is for categorical variables equivalent to variance 
 for continuous variables . note that several variable categories overlapped near the 
 origin of the axes and are not labelled . variables describing food supply and consumption showed potential associations between food 
 prepared outside the home , age and season . the youngest ( 0 to < 5 years ) and the 
 oldest ( 60 years ) respondents were the least likely to have eaten food prepared outside the 
 home . in addition , mca outputs highlighted two potential clusters : ( i ) males aged 15 to 
 < 30 years and autumn with a possible association with consuming food purchased at a 
 food vendor or eat - in cafeteria , and ( ii ) respondents aged 35 to < 45 years and spring 
 with a possible association with the consumption of ready - to - eat foods or foods purchased at 
 a delicatessen . this study provides estimates of the occurrence of potential exposures commonly associated 
 with enteric infections in a sample of healthy individuals in a canadian community . it fills 
 an important knowledge gap related to the potential routes of exposure to enteric pathogens . the non - foodborne routes have been explored as well as the foodborne route through the 
 perspective of its origin , in the sense of where it was purchased ( e.g. directly from farm , 
 from hunting , from restaurants ) , and through the consumption of a few high - risk foods ( e.g. 
 unpasteurized or undercooked food ) . this allows completing the existing knowledge on the 
 exposures through specified food items . for 
 most of these exposures , < 15% of the population was exposed to that potential risk 
 during the recall period ( e.g. international travel , 24% ) . however , some of the measured 
 exposures were quite common ( e.g. eating food prepared outside the home , 78% ; attending a 
 social gathering , 35% ) . this information from the healthy population is important for 
 estimating baseline exposures for risk assessments and for identifying potential sources in 
 case - control studies or disease clusters and outbreak situations . for example , 
 exposure to recreational waters was more frequent in children and young teenagers ( 5 to 
 < 15 years ) and in adults aged 30 to < 45 years , whereas the oldest respondents 
 ( 60 ) were less exposed . however , 
 for household - level questions , the impact of gender should be interpreted with caution , as a 
 household can comprise several persons of both genders that all may influence the occurrence 
 of that exposure . considering that incidence of gastrointestinal illness usually varies by 
 age and gender , any comparison of these exposures with healthy controls should consider age 
 and gender . our results also assess the seasonal variation for some activities that may put people at 
 risk for contamination by enteropathogens . some behaviours were more frequent during summer 
 ( e.g. drinking bottled water , swimming , outdoor activities , gardening , barbecuing ) or less 
 frequent during winter or spring ( e.g. attending social gatherings , purchasing food at 
 farmers ' market or farm laneway ) . these observations reveal the impact of the climate of 
 this region of canada ( cold and snowy winter , hot and humid summer ) on behaviours and 
 habits . the observed seasonality for some exposures , however , is difficult to explain by the 
 climate and may be spurious ( e.g. higher frequency of eating delicatessen food in autumn , 
 lower frequency in winter of municipal water as source of drinking water ) . including the 
 seasonal pattern of potential risk factors for comparisons of cases of infectious diseases 
 with healthy controls is important as most infectious gastrointestinal disorders show a 
 clear seasonality in canada and in temperate countries . there is a summer peak in bacterial 
 disease incidence ( campylobacteriosis , salmonellosis or pathogenic escherichia 
 coli infections ) [ 1721 ] and an increased incidence in winter for viral diseases ( norovirus 
 and rotavirus infections ) [ 2225 ] . the 
 periodicity , or time between exposures , can be used in exposure assessment models , to rank 
 relative risks by individual behaviour occurrence ( yes / no ) and to assess the frequency 
 ( inverse of the periodicity ) of exposures . to estimate the periodicity , we looked at the 
 differences in the exposure rates obtained for three recall periods , a factor that is 
 important in understanding both disease outcomes and behaviour profiles in the study 
 population [ 26 , 27 ] . for a few exposures , the occurrence significantly increased with the length 
 of recall period , allowing estimation of periodicity of the exposure . however , most of the 
 time the exposure rates were not significantly different across the three recall period 
 groups , meaning that the exposure was either constant ( e.g. contact with pets ) or that the 
 differences between recall periods could not be detected with our sample size . for example , 
 there was no significant difference in exposures across the three recall periods ( 3 , 7 , 14 
 days ) for international travel ( 17% , 21% , 34% , respectively ) but it is unlikely its 
 periodicity is <3 days . in this case of a rare exposure the lack of difference between the three recall 
 periods for some exposures could also be attributable to recall bias , although it is 
 unlikely for exposures such as international travel . future studies could include groups 
 with a longer recall period ( e.g. 21 and 28 days ) to help more precisely quantify the 
 periodicity of a greater number of exposures and provide exposure information for diseases 
 that have long incubation periods such as cryptosporidiosis or giardiasis . however , it has 
 been shown that recall bias is likely to increase with the length of the recall period 
 [ 28 , 29 ] . another limitation to assessing periodicity relates to the absence of questions 
 on the number of times the exposure occurred during the recall period ( or if the exposure 
 was constant ) . finally , it should be noted that for seasonal activities such as gardening and canoeing , the 
 actual frequency of exposure might be diluted when considering an entire year to assess the 
 exposure . it may be worth restricting the assessment of the exposure frequency of seasonal 
 activities to the appropriate seasons . beyond the inherent biases due to language restriction and selection of the source 
 population from a telephone list , there were biases due to interview error during 
 recruitment of respondents during september  december which led to an increased number of 
 interviews in summer ( july  august ) . this error may have influenced the capacity to detect 
 the impact of season on certain exposures . however , when considering the perspective of 
 using those data in the frame of a case - control study , for which the controls would be 
 matched with the cases on the date , additional controls are available for the summer period 
 when most of the diseases are peaking . the results presented herein about several exposure behaviours of healthy people are a rich 
 source of information for the design of future research studies , for refining hypotheses 
 related to the transmission of enteric diseases in a canadian community , from farm - to - fork 
 or source - to - tap and for understanding the effect of varying recall periods on exposure 
 measurements . these results can be used for case - control studies , exposure assessment 
 studies as well as informing attribution modelling efforts and developing quantitative 
 microbial risk assessments .
summaryinformation is lacking in canada on the frequency of exposures of healthy people to 
 enteric pathogen sources ( i.e. water , food , animal contact ) at the community level . 
 this 
 information is critical to develop more robust risk assessments and prioritize control 
 measures . 
 a 12-month - long cross - sectional telephone survey of 1200 healthy individuals in 
 a sentinel community was performed . 
 survey respondents were divided into three recall 
 period groups ( 3 , 7 , 14 days ) . 
 the occurrence of 46 exposures ( including water , animal 
 contact , environmental contact and high - risk foods ) was assessed per recall period . 
 effect 
 of age , gender , and season on exposures was modelled and frequencies of exposure were 
 extrapolated . 
 thirty - five exposures had similar occurrences across recall periods . 
 age was 
 significant for 23 exposures , season for 18 , and gender for three . 
 exposures that vary by 
 age and season ( i.e. bottled water , swimming , etc . ) 
 warrant consideration when 
 investigating and analysing cases of enteric illness .