View of Transmission of SARS-CoV-2: A iReview

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11703 http://annalsofrscb.ro

Transmission iof iSARS-CoV-2: iA iReview

1Jyothi iK iand i^{2 i}Krishna iPrasad iM

1Department iof iMicrobiology, iAndhra iUniversity, iVisakhapatnam, iIndia.

2 iDepartment iof iChemical iEngineering, iGMR iInstitute iof itechnology, iGMR iNagar, iRajam, iIndia.

Corresponding iAuthor: [email protected]

Abstract

The iWorld iHealth iOrganization irecognized iSARS-CoV-2 ias ia ipublic ihealth iconcern iand ideclared iit ias ia ipandemic ion iMarch i11, i2020. iOver i12 imillion ipeople ihave ibeen iaffected iacross iseveral icountries isince iit iwas ifirst irecognized. iSARS-CoV-2 iis ithought ito icommonly ispread ithrough irespiratory idroplets iformed iwhile italking, icoughing, iand isneezing iof ian iinfected ipatient. Broadly, itwo imodes iof itransmission iof iCOVID-19 iexist idirect iand iindirect. iThe idirect imode iincludes itransmission ivia iaerosols iformed ithrough isurgical iand idental iprocedures iand/or iin ithe iform iof irespiratory idroplet inuclei; iother ibody ifluids iand isecretions isuch ias ifeces, isaliva, iurine, isemen, iand itears; imother-to-child. iIndirect itransmission imay ioccur ithrough ifomites ior isurfaces ipresent iwithin ithe iimmediate ienvironment iof ian iinfected ipatient iand iobjects iused iby ithe iinfected iperson. iAs imany iof ithese imodes imay ibe iunderestimated, iit iis inecessary ito iemphasize iand iillustrate ithem.

iUnderstanding ihow, iwhen iand iin iwhich isettings iinfected ipeople itransmit ithe ivirus iis iimportant ifor ideveloping iand iimplementing icontrol imeasures ito ibreak ichains iof itransmission.The iaim iof ithis ipaper iis ito ibriefly ireview ihow iSARS-CoV-2 itransmit ivia ivarious imodes iand ipropose imeasures ito ireduce ithe irisk iof ispread iwithin ithe ipopulation. i

Key iwords: iAerosols, iCOVID-19, iDroplets, iSARS-CoV-2, iTransmission, iPopulations, i Introduction

Severe iacute irespiratory isyndrome icoronavirus i2 i(SARS-CoV-2), ithe ietiologic iagent iof icoronavirus idisease i2019 i(COVID-19), ihas ispread iworldwide iin ia ifew imonths. iThis iarticle ipresents ia icomprehensive ireview iof ithe iconfirmation ion itransmission iof ithis ivirus.

iAlthough iseveral iexperimental istudies ihave icultured ilive ivirus ifrom iaerosols iand isurfaces ihours iafter iinoculation. iStrong ievidence ifrom icase iand icluster ireports isuggests ithat irespiratory ispread iis idominant, iwith iproximity iand iventilation ibeing ikey ideterminants iof itransmission ithreat. iIn ithe ifew icases iwhere idirect icontact ior ifomite itransmission iis ipresumed, irespiratory itransmission ihas inot ibeen icompletely iomitted. iThe ivirus ihas ivaried itransmission idynamics: iMost ipersons ido inot itransmit ivirus, iwhereas isome icause isecondary icases iin itransmission iclusters icalled i“superspreading ievents.” iEvidence-based ipractices ishould iincorporate ithe iaccumulating iknowledge iabout itransmission iof iSARS-CoV-2 ito ihelp

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iinstruct ithe ipublic iand islow ithe ispread iof ithis ivirus.

This iscientific ireview ipresents ithe iconsolidation iof ireviews iof ipublications iin ipeer-reviewed ijournals iundertaken iby iWHO iand ipartners. iCurrent ievidence isuggests ithat iSARS-CoV-2, ithe ivirus ithat icauses iCOVID-19, iis ipredominantly ispread ifrom iperson-to- person. iUnderstanding ihow, iwhen iand iin iwhat itypes iof isettings iSARS-CoV-2 ispreads iis icritical ito idevelop ieffective ipublic ihealth iand iinfection iprevention iand icontrol imeasures ito ibreak ichains iof itransmission.

Modes iof itransmission

This ireview inarrates ipossible imethods iof itransmission ifor iSARS-CoV-2, iincluding icontact, idroplet, iairborne, ifomite, ifecal-oral, ibloodborne, imother-to-child, iand ianimal-to- human itransmission. iInfection iwith iSARS-CoV-2 iprimarily icauses irespiratory iillness iranges ifrom imild idisease ito isevere idisease iand ideath, iand isome ipeople iinfected iwith ithe ivirus inever idevelop isymptoms. i

i) iContact iand idroplet itransmission

Transmission iof iSARS-CoV-2 ican ioccur ithrough idirect, iindirect, ior iclose icontact iwith iinfected ipeople ivia iinfected isecretions isuch ias isaliva iand irespiratory isecretions ior itheir irespiratory idroplets, iwhich iare iexpelled iwhen ian iinfected iperson icoughs, isneezes, italks ior isings i(Liu iet ial.,2020; iChan iet ial.,2020; iHuang iet ial.,2020; iBurke iet ial.,2020). i

iRespiratory idroplets iare i>5-10 iμm iin idiameter iwhereas idroplets i<5μm iin idiameter iare ireferred ito ias idroplet inuclei ior iaerosols i(Ghinai iet ial.,2020). i iRespiratory idroplet itransmission ican ioccur iwhen ia iperson iis iin iclose icontact i(within i1 imetre) iwith ian iinfected iperson iwho ihas irespiratory isymptoms i(e.g. icoughing ior isneezing) ior iwho iis italking ior isinging i(Pung iet ial.,2020). i iIn ithese icircumstances, irespiratory idroplets ithat iinclude ivirus ican ireach ithe imouth, inose ior ieyes iof ia isusceptible iperson iand ican iresult iin iinfection. iIndirect icontact itransmission iinvolving icontact iof ia isusceptible ihost iwith ia icontaminated iobject ior isurface i(fomite itransmission) imay ialso ibe ipossible.

ii) iAirborne itransmission

Airborne itransmission iis idefined ias ithe ispread iof ian iinfectious iagent icaused iby ithe idistribution iof idroplet inuclei i(aerosols) ithat iremain iinfectious iwhen ipresent iin iair iover ilong idistances iand itime. iAirborne itransmission iof iSARS-CoV-2 ican ioccur iduring imedical iprocedures ithat igenerate iaerosols i(“aerosol igenerating iprocedures”). iWHO, itogether iwith ithe iscientific icommunity, ihas ibeen iactively ievaluating iwhether iSARS-CoV-2 imay ialso ispread ivia iaerosols iin ithe iabsence iof iaerosol igenerating iprocedures, iparticularly iin iindoor isettings iwith ipoor iventilation.The iphysics iof iexhaled iair iand iflow iphysics ihave igenerated ihypotheses iabout ipossible imechanisms iof iSARS-CoV-2 itransmission ithrough iaerosols

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i(Mittal ietal.,2020; iBourouiba iet ial.,2020). iThese itheories isuggest ia inumber iof irespiratory idroplets igenerate imicroscopic iaerosols i(<5 iµm) iby ievaporating, iand inormal ibreathing iand italking iresults iin iexhaled iaerosols. iThus, ia isusceptible iperson icould iinhale iaerosols, iand icould ibecome iinfected iif ithe iaerosols icontain ithe ivirus iin isufficient iquantity ito icause iinfection iwithin ithe irecipient. iHowever, ithe iproportion iof iexhaled idroplet inuclei ior iof irespiratory idroplets ithat ievaporate ito igenerate iaerosols, iand ithe iinfectious idose iof iviableiSARS-CoV-2 irequired ito icause iinfection iin ianother iperson iare inot iknown, ibut iit ihas ibeen istudied ifor iother irespiratory iviruses i(Gralton iet ial., i2013).

Stadnytskyi iet ial.,2020 iobserved ithe iamount iof idroplets iof ivarious isizes ithat iremain iairborne iduring inormal ispeech iin ihis iexperimental istudy. iHowever, ithe iauthors iacknowledge ithat ithis ihas inot ibeen ivalidated ifor ihumans iand iSARS-CoV-2. iSomsen iet ial.,2020 ifound ithat ihealthy iindividuals ican iproduce iaerosols ivia icoughing iand italking i, iand ianother imodel irecommended ihigh ivariability ibetween iindividuals iin iterms iof iparticle iemission irates iduring ispeech, iwith iincreased irates icorrelated iwith iincreased iamplitude iof ivocalization i(Asadi iet ial.,2020). iTo idate, ispread iof iSARS-CoV-2 iby ithis itype iof iaerosol iroute ihas inot ibeen idemonstrated. iExperimental istudies iconducted iby iVan iet ial i.,2020 iand iFears iet ial.,2020 ihave igenerated iaerosols iof iinfectious isamples iusing ihigh-powered ijet inebulizers iunder icontrolled ilaboratory iconditions. iThese istudies ifound iSARS-CoV-2 ivirus iRNA iin iair isamples iwithin iaerosols ifor iup ito i3 ihours iin ione istudy i(Van iet ial i., i2020) i iand i16 ihours iin ianother, iwhich ialso ifound iviable ireplication-competent ivirus i(Fears iet ial.,2020). iThese ifindings iwere ifrom iexperimentally iinduced iaerosols ithat ido inot ireflect inormal ihuman icough iconditions.

Chia i,2020; iGuo ietal.,2020 iand i iLiu iet ial.,2020 iconducted istudies iin ihealth icare isettings iwhere isymptomatic iCOVID-19 ipatients iwere icared ifor, ibut iwhere iaerosol igenerating iprocedures iwere inot iperformed, ireported ithe ipresence iof iSARS-CoV-2 iRNA iin iair isamples. iWithin isamples iwhere iSARS-CoV-2 iRNA iwas ifound, ithe iquantity iof iRNA idetected iwas iin iextremely iless inumbers iin ilarge ivolumes iof iair iand ione istudy ithat ifound iSARS-CoV-2 iRNA iin iair isamples ireported iinability ito iidentify iviable ivirus i(Santarpia iet ial.,2020). i iThe idetection iof iRNA iusing ireverse itranscription ipolymerase ichain ireaction i(RT-PCR)-based iassays iis inot inecessarily iindicative iof ireplication- iand iinfection-competent ivirus ithat icould ibe itransmissible iand icapable iof icausing iinfection i(Bullard iet ial.,2020).

Recent iclinical ireports iof ihealth iworkers iexposed ito iCOVID-19 icases, ifound ino inosocomial itransmission iwhen icontact iand idroplet iprecautions iwere iappropriately iused,iincluding ithe iwearing iof imedical imasks ias ia icomponent iof ithe ipersonal iprotective iequipment i(PPE) i(Durante iet ial.,2020; iWong iet ial.,2020). i iThese iobservations isuggest ithat iaerosol itransmission idid inot ioccur iin ithis icontext. iFurther istudies iare ineeded ito idetermine iwhether iit iis ipossible ito idetect iviable iSARS-CoV-2 iin iair isamples ifrom isettings iwhere ino iprocedures ithat igenerate iaerosols iare iperformed iand iwhat irole iaerosols imight iplay iin itransmission.

Some ioutbreak ireports irelated ito iindoor icrowded ispaces i(Leclerc iet ial.,2020) ihave

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isuggested ithe ipossibility iof iaerosol itransmission, icombined iwith idroplet itransmission, ifor iexample, iduring ichoir ipractice i(Hamner iet ial.,2020), iin irestaurants i(Lu i iet ial.,2020) ior iin ifitness icentres i(Jang i iet ial.,2020). iHowever, ithe idetailed iinvestigations iof ithese iclusters iwhere ishort-range iaerosol itransmission, iparticularly iin ispecific iindoor ilocations, isuch ias icrowded iand iinadequately iventilated ispaces iover ia iprolonged iperiod iof itime iwith iinfected ipersons isuggest ithat idroplet iand ifomite itransmission icould iexplain ihuman-to-human itransmission. iFurther, ithe iclose icontact ienvironments iof ithese iclusters imay ihave ifacilitated itransmission ifrom ia ismall inumber iof icases ito imany iother ipeople i(e.g., isuperspreading ievent), iespecially iif ihand ihygiene iwas inot iperformed iand imasks iwere inot iused iwhen iphysical idistancing iwas inot imaintained i(Adam iet ial.,2020).

iii) iFomite itransmission

Respiratory isecretions ior idroplets iexpelled iby iinfected iindividuals ican icontaminate isurfaces iand iobjects, icreating ifomites i(contaminated isurfaces) i(Van iet ial.,2020; iGuo iet ial.,2020). iViable iSARS-CoV-2 ivirus ior iRNA idetected iby iRT-PCR ican ibe ifound ion ithose isurfaces ifor iperiods iranging ifrom ihours ito idays, idepending ion ithe itemperature iand ihumidity iand ithe itype iof isurface i(Zhou iet ial.,2020). iViable iSARS-CoV-2 ivirus ior iRNA iare iat ihigh iconcentration iin ihealth icare ifacilities iwhere iCOVID-19 ipatients iwere ibeing itreated i( iMa iet ial., i2020; iOng iet ial.,2020)ⁱHence, itransmission imay ialso ioccur iindirectly ivia itouching isurfaces iin ithe iimmediate ienvironment ior iobjects icontaminated iwith ivirus ifrom ian iinfected iperson i(e.g. istethoscope ior ithermometer), ifollowed iby itouching itheimouth, inose, ior ieyes i(Dohla iet ial.,2020). iFomite itransmission iis iconsidered ia ilikely imode iof itransmission ifor iSARS-CoV-2, igiven iconsistent ifindings iabout ienvironmental icontamination iin ithe ivicinity iof iinfected icases iand ithe ifact ithat iother icoronaviruses iand irespiratory iviruses ican itransmit ithis iway i(Pastorino iet ial.,2020; iMatson iet ial.,2020).

iv) iOther imodes iof itransmission

Guan iet ial.,2020; iPan iet ial.,2020; iWang iet ial.,2020; iWu iet ial.,2020 iand iZheng iet ial.,2020 idetected iSARS-CoV-2 iRNA iin iother ibiological isamples, iincluding ithe iurine iand ifeces iof isome ipatients. iSun iet ial., i2020 inoticed iviable iSARS-CoV-2 iin ithe iurine iof ione ipatient. iXiao iet ial.,2020 iand iZhang iet ial.,2020 ihave icultured iSARS-CoV-2 ifrom istool ispecimens. i iTo idate, ihowever, ithere ihave ibeen ino ipublished ireports iof itransmission iof iSARS-CoV-2 ithrough ifeces ior iurine. i

Chang iet ial.,2020 ihave ireported idetection iof iSARS-CoV-2 iRNA, iin ieither iplasma ior iserum, iand ithe ivirus ican ireplicate iin iblood icells. iHowever, ithe irole iof iblood iborne itransmission iremains iuncertain; iand ilow iviral ititers iin iplasma iand iserum isuggest ithat ithe irisk iof itransmission ithrough ithis iroute imay ibe ilow. iAt ipresent, ithere iis ino ievidence ifor iintrauterine itransmission iof iSARS-CoV-2 ifrom iinfected ipregnant iwomen ito itheir ifetuses, ialthough idata iremain ilimited. iWHO ihas irecently ipublished ia iscientific ibrief ion ibreastfeeding iand iCOVID-19.ⁱThis ibrief iexplains ithat iviral iRNA ifragments ihave ibeen ifound iby iRT-PCR itesting iin ia ifew ibreast imilk isamples iof imothers iinfected iwith iSARS-

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CoV-2. iTransmission iof iSARS-CoV-2 ifrom imother ito ichild iwould inecessitate iinfectious ivirus iin ibreast imilk ibeing iable ito ireach itarget isites iin ithe iinfant iand ialso ito iovercome iinfant idefense isystems. iWHO irecommends ithat imothers iwith isuspected ior iconfirmed iCOVID-19 ishould ibe iencouraged ito iinitiate ior icontinue ito ibreast ifeed.

Evidence ito idate ishows ithat iSARS-CoV-2 iis imost iclosely irelated ito iknown ibetacoronaviruses iin ibats; ithe irole iof ian iintermediate ihost iin ifacilitating itransmission iin ithe iearliest iknown ihuman icases iremains iunclear i(Andersen iet ial.,2020; iZhou iet ial.,2020). i iCurrent ievidence isuggests ithat ihumans iinfected iwith iSARS-CoV-2 ican iinfect iotherimammals, iincluding idogs, icats, iand ifarmed imink. iHowever, iit iremains iunclear iif ithese iinfected imammals ipose ia isignificant irisk ifor itransmission ito ihumans i(Sit iet ial.,2020;

iNewman., i2020; iOreshkova iet ial., i2020).

v) iSpread iof iSARS-CoV-2 ifrom iinfected iperson ito iothers

Knowing iwhen ian iinfected iperson ican ispread iSARS-CoV-2 iis ijust ias iimportant ias ihow ithe ivirus ispreads. iEvidence isuggests ithat iSARS-CoV-2 iRNA ican ibe idetected iin ipeople i1-3 idays ibefore itheir isymptom ionset, iwith ithe ihighest iviral iloads, ias imeasured iby iRT-PCR, iobserved iaround ithe iday iof isymptom ionset, ifollowed iby ia igradual idecline iover itime i(Pan iet ial.,2020; iHe iet ial.,2020; iZou iet ial.,2020; iTo iet ial.,2020 iand iWolfel iet ial.,2020). iThe iduration iof iRT-PCR ipositivity igenerally iappears ito ibe i1-2 iweeks ifor iasymptomatic ipersons, iand iup ito i3 iweeks ior imore ifor ipatients iwith imild ito imoderate idisease i(Zhou iet ial.,2020; i iXu iet ial.,2020). iIn ipatients iwith isevere iCOVID-19 idisease, iit ican ibe imuch ilonger i(Pan iet ial.,2020).

Detection iof iviral iRNA idoes inot inecessarily imean ithat ia iperson iis iinfectious iand iable ito itransmit ithe ivirus ito ianother iperson. iStudies iusing iviral iculture iof ipatient isamples ito iassess ithe ipresence iof iinfectious iSARS-CoV-2 iare icurrently isparse. i iBriefly, iviable ivirus ihas ibeen iisolated ifrom ian iasymptomatic icase, ifrom ipatients iwith imild ito imoderate idisease iup ito i8-9 idays iafter isymptom ionset, iand ifor ilonger ifrom iseverely iill ipatients i(Arons iet ial.,2020). iAdditional istudies iare ineeded ito idetermine ithe iduration iof iviable ivirus ishedding iamong iinfected ipatients. i

vi) iTransmission iof iSARS-CoV-2 ivia idroplets iand iclose icontact

SARS-CoV-2 ispreads ivia idroplets iand iclose icontact iwith iinfected isymptomatic icases. i iIn ian ianalysis iof i76,005 iCOVID-19 icases iin iChina, i80% iof iclusters ioccurred iwithin ihousehold isettings, isuggesting ithat itransmission ioccurs iduring iclose iand iprolonged icontact. iA istudy iof ithe ifirst ipatients iin ithe iRepublic iof iKorea ishowed ithat i9 iof i13 isecondary icases ioccurred iamong ihousehold icontacts i(Park iet ial.,2020). iOutside iof itheihousehold isetting, ithose iwho ihad iclose iphysical icontact, ishared imeals, ior iwere iin ienclosed ispaces ifor iapproximately ione ihour ior imore iwith isymptomatic icases, isuch ias iin iplaces iof iworship, igyms, ior ithe iworkplace, iwere ialso iat iincreased irisk iof iinfection i(James iet ial.,2020). iOther ireports ihave isupported ithis iwith isimilar ifindings iof isecondary

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itransmission iwithin ifamilies iin iother icountries i(Wei iet ial.,2020).

vii) i iTransmission iof iSARS-CoV-2 ifrom iSARS-CoV-2 iinfected ipersons iwithout isymptoms

Preliminary idata ifrom iChina irecommended ithat ipeople iwithout isymptoms icould iinfect iothers. iTo ibetter iunderstand ithe irole iof itransmission ifrom iinfected ipeople iwithout isymptoms, iit iis iimportant ito idistinguish ibetween itransmission ifrom ipeople iwho iare iinfected iwho inever idevelop isymptoms i(asymptomatic itransmission) iand itransmission ifrom ipeople iwho iare iinfected ibut ihave inot ideveloped isymptoms iyet i(pre-symptomatic itransmission). iThis idistinction iis iimportant iwhen ideveloping ipublic ihealth istrategies ito icontrol itransmission.The iproportion iof ipeople iwhose iinfection iis iasymptomatic ilikely ivaries iwith iage idue ito ithe iincreasing iprevalence iof iunderlying iconditions iin iolder iage igroups iand ithus iincreasing irisk iof ideveloping isevere idisease iwith iincreasing iage, iand istudies ithat ishow ithat ichildren iare iless ilikely ito ishow iclinical isymptoms icompared ito iadults i(Davies iet ial.,2020). iKimball iet ial.,2020 iand iWang iet ial., i2020 iinformed ithat imany icases iwere iasymptomatic, ibased ion ithe ilack iof isymptoms iat ithe itime iof itesting, ihowever, i75-100%

iof ithese ipeople ilater ideveloped isymptoms. iMultiple istudies ihave ishown ithat ipeople iinfect iothers ibefore ithey ithemselves ibecame iill i(Luo iet ial.,2020; iJang iet ial.,2020; iArons iet ial.,2020).

Transmission ifrom iinfected ipeople iwithout isymptoms iis idifficult ito istudy. iHowever, iinformation ican ibe igathered ifrom idetailed icontact itracing iefforts, ias iwell ias iepidemiologic iinvestigations iamong icases iand icontacts. iRecent isystematic ireviews isuggests ithat iindividuals iwithout isymptoms iare iless ilikely ito itransmit ithe ivirus ithan ithose iwho idevelop isymptoms i(Wang iet ial.,2020; iLuo iet ial.,2020). i

Suggestions ifor ipreventing itransmission

It iis iclear ifrom iavailable ievidence iand iexperience, ithat ilimiting iclose icontact ibetween iinfected ipeople iand iothers iis icentral ito ibreaking ichains iof itransmission iof ithe ivirus icausing iCOVID-19. iThe iprevention iof itransmission iis ibest iachieved iby iidentifying isuspect icases ias iquickly ias ipossible, itesting, iand iisolating iinfectious icases i(Lauer iet ial.,2020). iIn iaddition, iit iis icritical ito iidentify iall iclose icontacts iof iinfected ipeople iso ithat ithey ican ibe iquarantined ito ilimit ionward ispread iand ibreak ichains iof itransmission. iBy iquarantining iclose icontacts, ipotential isecondary icases iwill ialready ibe iseparated ifrom iothers ibefore ithey idevelop isymptoms ior ithey istart ishedding ivirus iif ithey iare iinfected, ithus ipreventing ithe iopportunity ifor ifurther ionward ispread. iThe iincubation iperiod iof iCOVID-19, iwhich iis ithe itime ibetween iexposure ito ithe ivirus iand isymptom ionset, iis ion iaverage i5-6 idays, ibut ican ibe ias ilong ias i14 idays i(Yu iet ial.,2020). iThus, iquarantine ishould ibe iin iplace ifor i14 idays ifrom ithe ilast iexposure ito ia iconfirmed icase. iIf iit iis inot ipossible ifor ia icontact ito iquarantine iin ia iseparate iliving ispace, iself-quarantine ifor i14 idays iat ihome iis irequired; ithose iin iself-quarantine imay irequire isupport iduring ithe iuse iof iphysical idistancing

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imeasures ito iprevent ithe ispread iof ithe ivirus.

It iis igiven ithat iinfected ipeople iwithout isymptoms ican itransmit ithe ivirus, iit iis ialso iprudent ito iencourage ithe iuse iof ifabric iface imasks iin ipublic iplaces iwhere ithere iis icommunity itransmission i(Mittal iet ial., i2020) iand iwhere iother iprevention imeasures, isuch ias iphysical idistancing, iare inot ipossible. iFabric imasks, iif imade iand iworn iproperly, ican iserve ias ia ibarrier ito idroplets iexpelled ifrom ithe iwearer iinto ithe iair iand ienvironment. iHowever, imasks imust ibe iused ias ipart iof ia icomprehensive ipackage iof ipreventive imeasures, iwhich iincludes ifrequent ihand ihygiene, iphysical idistancing iwhen ipossible, irespiratory ietiquette, ienvironmental icleaning iand idisinfection i(Wu iet ial.,2020). iRecommended iprecautions ialso iinclude iavoiding iindoor icrowded igatherings ias imuch ias ipossible, iin iparticular iwhen iphysical idistancing iis inot ifeasible, iand iensuring igood ienvironmental iventilation iin iany iclosed isetting.

WHO icontinues ito irecommend idroplet iand icontact iprecautions iwithin ihealth icare ifacilities iwhen icaring ifor iCOVID-19 ipatients iand iairborne iprecautions iwhen iand iwhere iaerosol igenerating iprocedures iare iperformed i(Alhazzani iet ial.,2020). iWHO ialso irecommends istandard ior itransmission-based iprecautions ifor iother ipatients iusing ian iapproach iguided iby irisk iassessment. iThese irecommendations iare iconsistent iwith iother inational iand iinternational iguidelines, iincluding ithose ideveloped iby ithe iEuropean iSociety iof iIntensive iCare iMedicine iand iSociety iof iCritical iCare iMedicine iand iby ithe iInfectious iDiseases iSociety iof iAmerica i(Lynch iet ial.,2020). i

Furthermore, iin iareas iwith iCOVID-19 icommunity itransmission, iWHO iadvises ithat ihealth iworkers iand icaregivers iworking iin iclinical iareas ishould icontinuously iwear ia imedical imask iduring iall iroutine iactivities ithroughout ithe ientire ishift.ⁱIn isettings iwhere iaerosol-generating iprocedures iare iperformed, ithey ishould iwear ian iN95, iFFP2 ior iFFP3 irespirator. iOther icountries iand iorganizations, iincluding ithe iUnited iStates iCenters ifor iDiseases iControl iand iPrevention i iand ithe iEuropean iCentre ifor iDisease iPrevention iand iControl i^{i i}recommend iairborne iprecautions ifor iany isituation iinvolving ithe icare iof iCOVID- 19 ipatients. i

Conclusions: i

The ioverarching iaim iof ithe iStrategic iPreparedness iand iResponse iPlan ifor iCOVID- 19 iis ito icontrol iCOVID-19 iby isuppressing itransmission iof ithe ivirus iand ipreventing iassociated iillness iand ideath. iTo ithe ibest iof iour iunderstanding, ithe ivirus iis iprimarily ispread ithrough icontact iand irespiratory idroplets. iUnder isome icircumstances iairborne itransmission imay ioccur i(such ias iwhen iaerosol igenerating iprocedures iare iconducted iin ihealth icare isettings ior ipotentially, iin iindoor icrowded ipoorly iventilated isettings ielsewhere). i iMore istudies iare iurgently ineeded ito iinvestigate isuch iinstances iand iassess itheir iactual isignificance ifor itransmission iof iCOVID-19.

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To iprevent itransmission, iWHO irecommends ia icomprehensive iset iof imeasures iincluding:

 Identifying isuspect icases ias iquickly ias ipossible, itest, iand iisolate iall icases iin iappropriate ifacilities;

 Identify iand iquarantine iall iclose icontacts iof iinfected ipeople iand itest ithose iwho idevelop isymptoms iso ithat ithey ican ibe iisolated iif ithey iare iinfected iand irequire icare;

 Use ifabric imasks iin ispecific isituations, ifor iexample, iin ipublic iplaces iwhere ithere iis icommunity itransmission iand iwhere iother iprevention imeasures, isuch ias iphysical idistancing, iare inot ipossible;

 Use iof icontact iand idroplet iprecautions iby ihealth iworkers icaring ifor isuspected iand iconfirmed iCOVID-19 ipatients, iand iuse iof iairborne iprecautions iwhen iaerosol igenerating iprocedures iare iperformed;

 Continuous iuse iof ia imedical imask iby ihealth iworkers iand icaregivers iworking iin iall iclinical iareas, iduring iall iroutine iactivities ithroughout ithe ientire ishift;

 At iall itimes, ipractice ifrequent ihand ihygiene, iphysical idistancing ifrom iothers iwhen ipossible, iand irespiratory ietiquette; iavoid icrowded iplaces, iclose-contact isettings iand iconfined iand ienclosed ispaces iwith ipoor iventilation; iwear ifabric imasks iwhen iin iclosed, iovercrowded ispaces ito iprotect iothers; iand iensure igood ienvironmental iventilation iin iall iclosed isettings iand iappropriate ienvironmental icleaning iand idisinfection.

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