WORLD TRADE G/SPS/GEN/53
20February 1998
ORGANIZATION(98-0602)
Original: English Committee onSanitary andPhytosanitary Measures
TRADE RESTRICTIONS INRESPONSE TOCHOLERA
Submission bytheWorld Health Organization
Thefollowing letter hasbeen received from theDirector-General oftheWorld Health
Organization (WHO) withtherequest thatitbemade available toallWTO Members.
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Thecurrent cholera epidemic inseveral African countries hascaused anumber ofcountries
toplace anembargo oncertain fishery products originating inthese African countries.
Thisistoinform youthatWHO, based onepidemiological evidence, advises itsMember States
todealwiththetheoretical riskofcholera transmission through international foodtradebymeans other
thanbyanembargo onimportation. Theattached FactSheet No.107,January 1998, oncholera has
beenissued inthiscontext. Inaddition, acircular letter toallMember States andAssociate Member
States ofWHO containing thisadvice willbesentoutinduecourse.G/SPS/GEN/53
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FactSheet No107
(Revised) January 1998
CHOLERA
Cholera isanacute intestinal infection caused bythebacterium Vibrio cholerae .Ithasashort
incubation period, fromlessthanonedaytofivedays, andproduces anenterotoxin thatcauses acopious,
painless, watery diarrhoea thatcanquickly leadtosevere dehydration anddeath iftreatment isnot
promptly given. Vomiting alsooccurs inmost patients.
Most persons infected withV.cholerae donotbecome ill,although thebacterium ispresent
intheirfaeces for7-14days. When illness doesoccur, more than90percentofepisodes areofmild
ormoderate severity andaredifficult todistinguish clinically from other types ofacute diarrhoea.
Lessthan10percentofillpersons develop typical cholera withsignsofmoderate orsevere dehydration.
Background
Thevibrio responsible fortheseventh pandemic, nowinprogress, isknown asV.cholerae 01,
biotype ElTor. Thecurrent seventh pandemic began in1961when thevibrio firstappeared asacause
ofepidemic cholera inCelebes (Sulawesi), Indonesia. Thedisease thenspread rapidly toothercountries
ofeastern Asiaandreached Bangladesh in1963, India in1964, andtheUSSR, IranandIraqin
1965-1966.
In1970 cholera invaded West Africa, which hadnotexperienced thedisease formore than
100years. Thedisease quickly spread toanumber ofcountries andeventually became endemic in
mostofthecontinent. In1991cholera struck Latin America, where ithadalsobeenabsent formore
thanacentury. Within theyearitspread to11countries, andsubsequently throughout thecontinent.
Until 1992, onlyV.cholerae serogroup 01caused epidemic cholera. Some other serogroups
could cause sporadic cases ofdiarrhoea, butnotepidemic cholera. Latethatyear, however, large
outbreaks ofcholera began inIndia andBangladesh thatwere caused byapreviously unrecognized
serogroup ofV.cholerae ,designated 0139, synonym Bengal. Isolation ofthisvibrio hasnowbeen
reported from10countries inSouth-East Asia. Itisstillunclear whether V.cholerae 0139willextend
toother regions, andcareful epidemiological monitoring ofthesituation isbeing maintained.
Transmission
Cholera isspread bycontaminated water andfood. Sudden largeoutbreaks areusually caused
byacontaminated water supply. Onlyrarely ischolera transmitted bydirect person-to-person contact.
Inhighly endemic areas, itismainly adisease ofyoung children, although breastfeeding infants are
rarely affected.
Vibrio cholerae isoften found intheaquatic environment andispartofthenormal floraof
brackish water andestuaries. Itisoftenassociated withalgalblooms (plankton), which areinfluenced
bythetemperature ofthewater. Human beings arealsooneofthereservoirs ofthepathogenic form
ofVibrio cholerae .
Treatment
When cholera occurs inanunprepared community, case-fatality ratesmaybeashighas50per
cent-usually because there arenofacilities fortreatment, orbecause treatment isgiven toolate. InG/SPS/GEN/53
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contrast, awell-organized response inacountry withawellestablished diarrhoeal disease control
programme canlimitthecase-fatality ratetolessthan1percent.
Most cases ofdiarrhoea caused byV.cholerae canbetreated adequately bygiving asolution
oforalrehydration salts(theWHO/UNICEF standard sachet). During anepidemic, 80-90 percent
ofdiarrhoea patients canbetreated byoralrehydration alone, butpatients whobecome severely
dehydrated must begiven intravenous fluids.
Insevere cases, aneffective antibiotic canreduce thevolume andduration ofdiarrhoea and
theperiod ofvibrio excretion. Tetracycline istheusual antibiotic ofchoice, butresistance toitis
increasing. Other antibiotics thatareeffective when V.cholerae aresensitive tothem include
cotrimoxazole, erythromycin, doxycycline, chloramphenicol andfurazolidone.
Epidemic Control andPreventive Measures
When cholera appears inacommunity itisessential toensure three things: hygienic disposal
ofhuman faeces, anadequate supply ofsafedrinking water, andgood foodhygiene. Effective food
hygiene measures include cooking foodthoroughly andeating itwhile stillhot;preventing cooked
foodsfrombeingcontaminatedbycontactwithrawfoods,includingwaterandice,contaminatedsurfaces
orflies; andavoiding rawfruits orvegetables unless theyarefirstpeeled. Washing hands after
defecation, andparticularly before contact withfoodordrinking water, isequally important.
Routine treatment ofacommunity withantibiotics, or"mass chemoprophylaxis", hasnoeffect
onthespread ofcholera, nordoesrestricting travel andtrade between countries orbetween different
regions ofacountry. Setting upacordon sanitaire atfrontiers usespersonnel andresources thatshould
bedevoted toeffective control measures, andhampers collaboration between institutions andcountries
thatshould unite theirefforts tocombat cholera.
Theonlycholera vaccine thatiswidely available atpresent iskilled vaccine administered
parenterally, which confers onlypartial protection (50percentorless)andforalimited period of
time(3-6months maximum). Useofthisvaccine toprevent orcontrol cholera outbreaks isnot
recommended because itmaygiveafalse sense ofsecurity tovaccinated subjects andtohealth
authorities, whomaythenneglect more effective measures.
In1973 theWHO World Health Assembly deleted fromtheInternational Health Regulations
therequirement forpresentation ofacholera vaccination certificate. Today, nocountry requires proof
ofcholera vaccination asacondition forentry, andtheInternational Certificate ofVaccination nolonger
provides aspecific space forrecording cholera vaccinations.
Limited stocks oftwooralcholera vaccines thatprovide high-level protection forseveral months
against cholera caused byV.cholerae 01haverecently become available inafewcountries. Both
aresuitable forusebytravellers buttheyhavenotyetbeenusedonalarge scale forpublic health
purposes.
Trade inFood Products Coming from Cholera-Infected Regions
Thepublication "Guidelines forCholera Control", available through WHO 'sDistribution and
Sales Unit, states thefollowing:
"Vibrio cholerae 01cansurvive onavariety offoodstuffs foruptofivedaysatambient
temperature andupto10daysat5-10degrees Celsius. Theorganism canalsosurvive freezing.G/SPS/GEN/53
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Lowtemperatures, however, limitproliferation oftheorganism andthusmayprevent thelevel
ofcontamination from reaching aninfective dose.
"Thecholera vibrio issensitive toacidity anddrying, andcommercially prepared acidic (ph4.5
orless)ordried foods aretherefore without risk. Gamma irradiation andtemperatures above
70degrees Celsius alsodestroy thevibrio andfoods processed bythese methods, according
tothestandards oftheCodex Alimentarius, andaresafeunless subsequently contaminated.
"The foods thatcause greatest concern toimporting countries areseafood andvegetables that
maybeconsumed raw.However, onlyrarecases ofcholera haveoccurred asaresult ofeating
food, usually seafood, transported across international borders byindividuals.
"...Indeed, although individual cases andclusters ofcases havebeenreported, WHO hasnot
documented asignificant outbreak ofcholera resulting from commercially imported food."
Insummary, although thereisatheoretical riskofcholera transmission withinternational food
trade, theweight ofevidence suggests thatthisriskisverysmall andcannormally bedealtwithby
means other thananembargo onimportation.
WHO believes thatthebestwaytodealwithfoodimports from cholera-affected areas isfor
importing countries toagree, withfoodexporters, ongoodhygienic practices which needtobefollowed
during foodhandling andprocessing toprevent, eliminate orminimize theriskofanypotential
contamination; andtosetuparrangements toobtain assurance thatthesemeasures areadequately carried
out.
Atpresent, WHO hasnoinformation thatfoodcommercially imported fromaffected countries
hasbeenimplicated inoutbreaks ofcholera inimporting countries. Theisolated cases ofcholera, that
havebeenrelated toimported food, havebeenassociated withfoodwhich hadbeeninthepossession
ofindividual travellers. Therefore, itmaybeconcluded thatfoodproduced under goodmanufacturing
practices poses onlyanegligible riskforcholera transmission. Consequently, WHO believes thatfood
import restrictions, based onthesolefactthatcholera isepidemic orendemic inacountry, arenot
justified.
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Forfurtherinformation,pleasecontactHealthCommuni cationsandPublicRelations,WHO,Geneva (4122)7912854.
Fax(4122)7914858.
AllWHO Press Releases, Facts Sheets andFeatures canbeobtained onInternet ontheWHO home page
http://www.who.ch/