Epidemiologic Characteristics of Foodborne Outbreaks in Southern Vietnam, 2009-2013

JMID/ 2017; 7 (1): 13-20 Jou nal o Mic obiology and In ec ious Diseases doi: 10.5799/ahinjs.02.2017.01.0247 Co espondence: D . Thuan Huu Vo, Uni e si y o Tampe e, School o Heal h Sciences, Depa men o Epidemiology, Tampe e, Finland, E-mail: [email p o ec ed] Recei ed: 14 June 2016, Accep ed: 26 Oc obe , 2016 Copy igh © JMID / Jou nal o Mic obiology and In ec ious Diseases 2017, All igh s ese ed RESEARCH ARTICLE Epidemiologic Cha ac e is ics o Foodbo ne Ou b eaks in Sou he n Vie nam, 2009–2013 Thuan Huu Vo1,2, Nguyen Nhu T an Minh3, Vinh Le2, Ninh Hoang Le2, Huy Quang Nguyen2, Tuan Van Le4, J. Pekka Nuo i1 1Uni e si y o Tampe e, School o Heal h Sciences, Depa men o Epidemiology, Tampe e, Finland 2Ins i u e o Public Heal h, Depa men o Planning and Technical Suppo , Ho Chi Minh Ci y, Vie nam 3Vie nam Field Epidemiology T aining P og am, Gene al Dep. o P e en i e Medicine, Minis y o Heal h, Hanoi, Vie nam 4Wo ld Heal h O ganiza ion Technical O ice, Ho Chi Minh Ci y, Vie nam ABSTRACT In oduc ion: Accu a e da a on he bu den o oodbo ne diseases (FBD) a e impo an o in o m p e en ion and con ol measu es. We desc ibed epidemiologic cha ac e is ics and assessed ends in oodbo ne ou b eaks in Sou he n Vie nam. Me hodology: We analyzed su eillance da a o ou b eaks epo ed in Sou he n Vie nam du ing 2009–2013. A FBD ou b eak is de ined as “ wo o mo e people who go gas oin es inal diso de a e ea ing he same meal o one a al case a e ea ing a meal”. Annual a es o ou b eaks/100,000 popula ion we e calcula ed; ends in ou b eaks we e assessed in ime-se ies analysis. Resul s: Du ing 2009-2013, he e we e 261 epo ed ou b eaks, 10,263 cases, and 50 dea hs; a e, 0.16 ou b eaks/100,000 popula ion/yea . O all ou b eaks, 77% occu ed in nine p o inces (popula ion 19.4 million) whe e expo manu ac u ing zones a e loca ed (2–8 ou b eaks/p o ince/yea ). O 212 ou b eaks in which epo e s had suspec ed an e iology, bac e ia accoun ed o 41%, na u al oxins o 20%, and unknown causes o 28%. Se en y- wo pe cen o all cases we e associa ed wi h meals ea en in can eens; 94% o cases li ed in he nine p o inces. Fou pe cen o all cases we e linked o amily meals; 85% o hese cases li ed in he u al Mekong Del a egion. All 50 a al cases we e a ibu ed o oxic chemicals o na u al oxins, 48 we e amily meals. Mos ou b eaks occu ed in wa me mon hs, bu no empo al end was seen in epo ed ou b eaks. Conclusions: The a e o epo ed ou b eaks and o al epo ed cases o FBD we e low, sugges ing unde de ec ion and unde epo ing. Mos iden i ied ou b eaks we e associa ed wi h meals ea en in can eens; a al cases we e linked o amily meals. J Mic obiol In ec Dis 2017; 7(1): 13-20 Keywo ds: Foodbo ne diseases, epidemiology, ou b eaks, su eillance, Vie nam INTRODUCTION In de eloping coun ies, oodbo ne diseases (FBD) su eillance sys ems a e o en subop imal; epidemiologic cha ac e is ics o FBD a e insu icien ly desc ibed, and mo bidi y and mo ali y due o FBD is p obably unde es ima ed [1]. In Vie nam, a ailable da a on FBD come p ima ily om oodbo ne ou b eak epo s [2]. The Vie nam Food Adminis a ion (VFA) and Food Sa e y Agencies (FSAs) gene ally ecei e epo s o ood poisonings o gas oen e i is ou b eaks when local epo e s suspec ansmission h ough ood. Mos ou b eaks a e de ec ed when se e e cases a e admi ed o heal h acili ies o when dea hs ha e occu ed. A ew e en s ha e been epo ed by dis ic hospi als, heal h wo ke s, o local esiden s while some e en s ha e been de ec ed om daily newspape epo s. Pee - e iewed publica ions ela ed o epidemiology o FBD in Vie nam a e sca ce. We desc ibed he epidemiologic cha ac e is ics and assessed ends o oodbo ne ou b eaks in Sou he n Vie nam om 2009 o 2013. 14 Vo TH, e al. Foodbo ne Ou b eaks in Sou he n Vie nam J Mic obiol In ec Dis www.jmidonline.o g Vol 7, No 1, Ma ch 2017 METHODS In Vie nam, na ional su eillance schemes ela ed o ood sa e y a e passi e. The su eillance sys ems o FBD a e unde he au ho i y o he VFA in Minis y o Heal h (MOH). In 2009, a FSA was es ablished in each o 63 p o inces o be esponsible o su eillance and con ol o FBD. Acco ding o cu en egula ions, all heal h o icials, public and p i a e heal h se ices a e esponsible o no i y FSAs a dis ic o p o incial le els when a suspec ed oodbo ne ou b eak occu s in hei se ing. When cases o FBD a e admi ed o a heal h acili y, he acili y has o epo o a highe -le el acili y and ul ima ely o he VFA. In se e e ou b eaks o hose associa ed wi h dea hs, p e en i e medicine se ices, heal h acili ies, o dis ic FSAs a e allowed o sha e da a/ epo s ou side hei ju isdic ion [3,4]. In 2013, he popula ion o 19 Sou he n p o inces o Vie nam was 33 million (37% o he o al popula ion o Vie nam) [5]. We analyzed ou ine su eillance da a o no i ied oodbo ne ou b eaks om hese p o inces du ing 2009–2013. A FBD ou b eak is de ined as “ wo o mo e people who go gas oin es inal diso de a e ea ing he same meal o one a al case a e ea ing a meal” [4]. The FSAs in Sou he n p o inces o Vie nam use a s anda d epo ing o m which includes he ollowing i ems: loca ion o ou b eak, implica ed meal and ood, pa ien ’s clinical signs and symp oms, causa i e agen s, numbe o exposed, cases, dea hs and hospi aliza ion by age g oups, samples aken om cases and oods o labo a o y analysis, en i onmen al inspec ions, as well as conclusions and ecommenda ions ela ed o he ou b eak. In es iga ed ou b eaks a e epo ed o he Ins i u e o Public Heal h in Ho Chi Minh Ci y [3]. Ca ego ized a iables we e desc ibed in equencies and p opo ions. Ra es we e calcula ed by using he o al annual ou b eaks du ing 2009-2013 di ided by mean popula ion o he egion/p o ince du ing he s udy pe iod. Time-se ies analysis was used o assess ends and seasonal ac o s in ou b eaks. Da a we e analyzed by using R so wa e ( se ies and o ecas packages). RESULTS Du ing 2009–2013, 261 oodbo ne ou b eaks we e epo ed in he 19 p o inces in Sou he n Vie nam. Annually, abou 2–8 oodbo ne ou b eaks we e epo ed in Ho Chi Minh Ci y (HCMC) and eigh p o inces a ound HCMC (Figu e 1A), accoun ing o 77% o all ou b eaks. The popula ion o HCMC and he eigh p o inces we e abou 7.5 and 11.9 million, espec i ely. The a e o gene al oodbo ne ou b eaks in Sou he n Vie nam was es ima ed a 0.16 pe 100,000-popula ion pe yea . Ra es o ou b eaks in p o inces a ound HCMC we e highe han hose in p o inces in Mekong Del a egion (Figu e 1B). O he 261 epo ed ou b eaks, 38% we e associa ed wi h can eens, 31% wi h amily meals and 18% wi h es au an s. Abou 7% o he ou b eaks occu ed in schools and 6% we e associa ed wi h s ee endo s. On a e age, app oxima ely 20 ou b eaks we e associa ed wi h can eens and 16 wi h amily meals annually in he egion (Figu e 2). O he 212 (81%) ou b eaks in which e iology was suspec ed, bac e ia we e pos ula ed in 87 (41%), na u al oxins in 42 (20%), and unknown/unde ined causes in 59 (28%) o he ou b eaks (Table 1). O he 49 (19%) ou b eaks in which e iology was con i med by labo a o y es s (labo a o y me hods we e based on he Vie nam Food Sa e y S anda d – app o ed by ISO/IEC 17025 – and he Associa ion o O icial Analy ical Chemis s in e na ional s anda ds o ood i ems), bac e ia (E. coli, S. au eus, Salmonella spp., B. ce eus, C. pe ingens, and Shigella spp.) accoun ed o 23 (47%), his amine o 17 (35%), chemicals (me hanol, ino ganochlo ine, o ganophospho us, ni a es, and oden icides) o 7 (14%), and e odo oxin o 2 (4%). In 181 (69%) ou b eaks links o speci ic oods we e sugges ed, bu hese we e no con i med by epidemiologic o labo a o y in es iga ion. The mos common suspec ed ood i ems we e po k (15%), una ish (13%), mul i- ing edien oods (12%), jelly ish (8%), alcohol con aining me hanol (7%), oad (6%), and pu e ish (6%). In each speci ic loca ion whe e oodbo ne ou b eaks occu ed, bac e ia we e suspec ed accoun o mos (33% in amily meals, 49% in la ge can eens, 65% in schools, 77% in 15 Vo TH, e al. Foodbo ne Ou b eaks in Sou he n Vie nam J Mic obiol In ec Dis www.jmidonline.o g Vol 7, No 1, Ma ch 2017 es au an s, and 84% in s ee endo s). The pe cen ages o unknown/unde ined causes we e 12% in s ee endo s, 16% in es au an s, 18% in amily meals, 25% in la ge can eens, and 35% in schools. Fo ou b eaks which occu ed in p i a e homes, na u al oxins accoun ed o 31% o ou b eaks (Figu e 3). Among 44 ou b eaks caused by na u al oxins, 91% we e associa ed wi h amily meals. O ou b eaks associa ed wi h chemicals, 61% (11) we e linked o amily meals. A o al o 10,263 cases we e pa o he epo ed ou b eaks. Abou 72% o cases had ea en hei meals a can eens in indus ial zones and 14% in es au an s, while only 5%, 4%, and 4% o cases we e associa ed wi h ou b eaks in o he loca ions (schools, s ee endo s, and amily meals, espec i ely) (Figu e 4). O he cases linked wi h can eens, 94% (6927) li ed in HCMC and he eigh su ounding p o inces al eady men ioned be o e. O he 428 cases associa ed wi h 82 ou b eaks occu ing a p i a e esidences, 85% (363) o cases we e in he u al Mekong Del a egion. The numbe o po en ially exposed pe sons (de ined as hose who a e he same meal as cases) was abou 78,000 du ing 2011–2013 (Table 1). O he 50 a al cases, 48 we e associa ed wi h amily meals, while one case was associa ed wi h s ee endo and one wi h a wedding pa y (Table 1). The implica ed oods in a al cases we e alcohol con aining me hanol (28), jelly ish (07), oad (07), pu e ish (06), and sea-c abs (02). In Figu e 5, he obse ed da a on ou b eak no i ica ions we e decomposed in o h ee componen s: end, seasonal, and andom/ esidual componen s. A e emo ing seasonal e ec s, no end was seen in epo ed ou b eaks du ing 2009–2013. The e we e mo e ou b eaks in 2010 han in he o he yea s. The numbe o ou b eaks pe mon h a ied by season and was highe du ing summe (highes in May) and lowe du ing win e (lowes in Decembe ). The mon hs wi h ewes ou b eaks we e Feb ua y–Ma ch and Augus -Decembe . Table 1. Baseline cha ac e is ics o he s udy popula ion. Ou b eak Yea s 2009 2010 2011 2012 2013 To al Numbe o epo ed ou b eaks 42 80 48 48 43 261 Numbe exposed NA NA 20,555 20,675 36,639 77,869 Numbe o cases 1,903 3,076 1,233 2,032 2,019 10,263 Numbe o dea hs 11 12 12 12 3 50 Numbe o suspec ed oods 35 62 32 26 26 181 Numbe o ou b eaks wi h suspec ed e iology 17 67 37 48 43 212 Bac e ia 3 30 19 15 20 87 Na u al oxins 3 9 11 9 10 42 Ro en ood 1 9 1 0 2 13 Chemicals 1 4 1 5 0 11 Unknown 9 15 5 19 11 59 Numbe o ou b eaks wi h con i med e iology 25 13 11 - - 49 Bac e ia 7 7 9 - - 23 Na u al oxins 0 2 0 - - 2 Ro en ood 16 1 0 - - 17 Chemicals 2 3 2 - - 7 16 Vo TH, e al. Foodbo ne Ou b eaks in Sou he n Vie nam J Mic obiol In ec Dis www.jmidonline.o g Vol 7, No 1, Ma ch 2017 Figu e 1. Annual numbe (A) and a e o oodbo ne ou b eaks pe 100,000 (B), Sou he n Vie nam, 2009–2013 Figu e 2. Annual numbe o ou b eaks by implica ed loca ion, Sou he n Vie nam, 2009–2013 Figu e 3. E iology o oodbo ne ou b eaks by place o occu ence, Sou he n Vie nam, 2009–2013 17 Vo TH, e al. Foodbo ne Ou b eaks in Sou he n Vie nam J Mic obiol In ec Dis www.jmidonline.o g Vol 7, No 1, Ma ch 2017 Figu e 4. Loca ion o oodbo ne ou b eaks and numbe o cases by yea , Sou he n Vie nam, 2009–2013 Figu e 5. Decomposi ion o addi i e ime-se ies o epo ed ou b eaks by yea , Sou he n Vie nam, 2009–2013 DISCUSSION Mos de ec ed ou b eaks and cases we e associa ed wi h can eens in HCMC and neighbo ing p o inces, whe e many expo manu ac u ing zones a e loca ed. In abou a hal o hese ou b eaks he suspec ed e iology was bac e ia and mo e han a qua e o suspec ed ood i ems con ained po k o we e mul i- 18 Vo TH, e al. Foodbo ne Ou b eaks in Sou he n Vie nam J Mic obiol In ec Dis www.jmidonline.o g Vol 7, No 1, Ma ch 2017 ing edien oods. This inding is consis en wi h ea lie epo s o ood poisonings o acu e gas oen e i is ou b eaks in he expo manu ac u ing zone can eens being associa ed wi h poo pe sonal hygiene and ime- empe a u e abuse du ing ood p epa a ion and se ing [6,7]. Tuna ish accoun ed o a conside able p opo ion o suspec ed oods. P ope handling and empe a u e con ol o una ish a e impo an o p e en simila ou b eaks, pa icula ly in he yea - ound ho wea he in Sou he n p o inces o Vie nam [8]. Ou b eaks associa ed wi h amily meals mainly occu ed in he Mekong Del a egion. Al hough he e we e ew cases, hese accoun ed o 96% o all epo ed a al cases. The a al cases we e caused by consump ion o coun e ei alcohol con aining me hanol o na u al oxins. I is clea ha alcohol sales should be con olled and heal h educa ion should be s eng hened o a oid consump ion o coun e ei alcohol and he common animals con aining na u al oxins. O e all, he e we e mo e ou b eaks in wa me mon hs (Figu e 5). The wa m and humid clima e in Sou he n Vie nam ( om 28°C o 35°C) enables mic oo ganisms o g ow and p oli e a e as e in con amina ed oods [9,10]. The highe numbe o ou b eaks du ing summe in 2010 could be ela ed o he highe empe a u e du ing he summe han o he yea s [11]. Au ho i ies o ood sa e y egula ly conduc wo in ensi ied inspec ions annually abou one mon h be o e mid-au umn es i al and luna New Yea ac oss Vie nam e e y yea . Fewe epo ed ou b eaks du ing Augus –Decembe and Feb ua y–Ma ch could be a esul o he inspec ions. Ou b eak no i ica ions only p o ide a c ude es ima e o he bu den o oodbo ne illness. The ou ine su eillance da abase in Sou he n Vie nam only included oodbo ne ou b eak epo s, p obably om se e e e en s. No demog aphic o epidemiologic in o ma ion was collec ed o indi idual cases. In addi ion, sel - medica ion wi h speci ic d ugs which can be ob ained wi hou p esc ip ion, could a ec de ec ion o ou b eaks. Because o hese easons, many mild ou b eaks may no ha e been no i ied o we e unde no i ied. I is likely ha he a e o ou b eaks and numbe o cases es ima ed om he su eillance da a a e likely an unde es ima ion. F om 2000 o 2010, a o al o 2,147 oodbo ne ou b eaks, 60,602 cases and 583 dea hs we e epo ed h oughou Vie nam; he incidence o cases was 6.9 pe 100,000 people pe yea . This was qui e low compa ed wi h o he coun ies in he egion, e.g., 47.8 pe 100,000 people in Malaysia and 67.8 pe 100,000 people in Thailand, and e en de eloped coun ies e.g., 290 pe 1000 people in Ne he land [12-15]. Mos iden i ied ou b eaks we e associa ed wi h can eens in expo manu ac u ing zones. Ou b eaks in his kind o se ings whe e he a ec ed coho is well de ined a e mo e likely o be de ec ed and in es iga ed han ou b eaks in which cases a e widely dispe sed in he communi y because o con amina ed comme cial p oduc s [16,17]. The e o e, de ec ion bias should be conside ed when in e p e ing he indings ela ed o he se ing o no i ied ou b eaks. Beside unde es ima ion and de ec ion bias, ou s udy has some limi a ions. Fi s , he da abase did no include in o ma ion o indi iduals and epo ing ime, so cha ac e is ics o cases and delays in epo could no be desc ibed. Second, incuba ion ime was no collec ed and mos implica ed oods we e pos ula ed, no con i med by epidemiologic in es iga ion. Thi d, mos causa i e agen s o he ou b eaks we e suspec ed on he basis o subjec i e assessmen s, no labo a o y e idence was p esen ed, and con ibu ing ac o s we e no documen ed. These indica e lack o applica ion o s anda d epidemiologic me hods in ou b eak in es iga ions making i di icul o assess which ac o s uly con ibu ed o he epo ed ou b eaks. Finally, he cu en su eillance sys em o oodbo ne diseases has low sensi i i y and capaci y o ea ly de ec ion o oodbo ne ou b eaks. To enable ea ly de ec ion, su eillance sys ems o FBD ha a e capable o eco ding/ e iewing no i ica ions and complain s om he public (no i ica ion/complain sys ems) and o collec ing in o ma ion on FBD symp oms (synd omic su eillance) should be conside ed. In addi ion, labo a o y capaci y should be s eng hened. Da a agg ega ion om he new and exis ing su eillance sys ems o FBD would enable be e es ima ion o FBD bu den and in o m e idence-based p e en ion and con ol measu es. 19 Vo TH, e al. Foodbo ne Ou b eaks in Sou he n Vie nam J Mic obiol In ec Dis www.jmidonline.o g Vol 7, No 1, Ma ch 2017 Conclusion The a e o epo ed ou b eaks and o al epo ed cases o FBD in Sou he n Vie nam we e low, sugges ing unde -de ec ion and unde epo ing. Mos iden i ied ou b eaks we e associa ed wi h can eens in expo manu ac u ing zones and could be linked o poo pe sonal hygiene and ime- empe a u e abuse [7]. Homemade ood ou b eaks mainly occu ed in u al a eas and associa ed wi h mos a al cases. P ope ood handling should be implemen ed in expo manu ac u ing zones and heal h educa ion on common poisonous animals should be s eng hened in u al a eas. Food sa e y inspec ions should be implemen ed egula ly h oughou he yea . App op ia e su eillance sys ems e.g., no i ica ion/complain sys ems and synd omic su eillance o FBD should be es ablished. Acknowledgemen s: We hank he Food Sa e y Agencies o 19 Sou he n P o inces o Vie nam which submi ed he ou b eak in es iga ion epo s. Funding: Uni e si y o Tampe e, School o Heal h Sciences suppo ed conduc ing his s udy. Decla a ion o con lic ing in e es s: The au ho s decla ed no con lic s o in e es wi h espec o he au ho ship and/o au ho ship o his a icle. REFERENCES 1. Wo ld Heal h O ganiza ion. WHO consul a ion o de elop a s a egy o es ima e he global bu den o oodbo ne diseases: aking s ock and cha ing he way o wa d. Gene a: Wo ld Heal h O ganiza ion 2006:1-27. 2. Vie nam Food Adminis a ion. 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