Screening of SARS-CoV-2 among homeless people, asylum-seekers and other people living in precarious conditions in Marseille, France, March–April 2020

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Screening of SARS-CoV-2 among homeless people,

asylum-seekers and other people living in precarious

conditions in Marseille, France, March–April 2020

Tran Ly, Nhu Nguyen, Van Hoang, Ndiaw Goumballa, Meriem Louni, Naomie

Canard, Thi Dao, Hacene Medkour, Audrey Borg, Kevin Bardy, et al.

To cite this version:

Tran Ly, Nhu Nguyen, Van Hoang, Ndiaw Goumballa, Meriem Louni, et al.. Screening of SARS-CoV-2

among homeless people, asylum-seekers and other people living in precarious conditions in Marseille,

France, March–April 2020. International Journal of Infectious Diseases, Elsevier, 2021, 105, pp.1 - 6.

�10.1016/j.ijid.2021.02.026�. �hal-03245839�

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Screening

of

SARS-CoV-2

among

homeless

people,

asylum-seekers

and

other

people

living

in

precarious

conditions

in

Marseille,

France,

March

–April

2020

Tran

Duc

Anh

Ly

a,b

,

Nhu

Ngoc

Nguyen

a,b

,

Van

Thuan

Hoang

a,b,c

,

Ndiaw

Goumballa

a,d

,

Meriem

Louni

a,b

,

Naomie

Canard

a,b

,

Thi

Loi

Dao

a,b,e

,

Hacene

Medkour

b,f

,

Audrey

Borg

b

,

Kevin

Bardy

b

,

Véra

Esteves-Vieira

b

,

Véronique

Filosa

b

,

Bernard

Davoust

b,f

,

Oleg

Mediannikov

b,f

,

Pierre-Edouard

Fournier

a,b

,

Didier

Raoult

a,b,f

,

Philippe

Gautret

a,b,

*

a

Aix-MarseilleUniversity,IRD,AP-HM,SSA,VITROME,Marseille,France

b

IHU-MéditerranéeInfection,Marseille,France

c

FamilyMedicineDepartment,ThaiBinhUniversityofMedicineandPharmacy,VietNam

d

VITROME,CampusInternationalIRD-UCADdel’IRD,Dakar,Senegal

e_Pneumology_Department,_Thai_Binh_University_of_Medicine_and_Pharmacy,_Viet_Nam

f_{Aix-Marseille}_University,_IRD,_AP-HM,_SSA,_MEPHI,_Marseille,_France

ARTICLE INFO Articlehistory: Received7December2020 Accepted5February2021 Keywords: COVID-19 SARS-CoV-2 Homelessness

Asylum-seekers,precariousconditions

Real-timepolymerasechainreaction

ABSTRACT

Background:Surveillanceofsevereacuterespiratorysyndromecoronavirus2(SARS-CoV-2)infection among shelteredhomeless andothervulnerable peoplemightprovide the informationneededto preventitsspreadwithinaccommodationcentres.

Methods:Datawereobtainedfrom698participantsindifferentaccommodationcentres(411homeless individuals,77asylum-seekers,58otherpeoplelivinginprecariousconditionsand 152employees working in these accommodation centres)who completedquestionnaires and had nasalsamples collectedbetween26Marchand17April2020.SARS-CoV-2carriagewasassessedbyquantitativePCR. Results:Wefoundahighacceptancerate(78.9%)fortesting.Overall,49people(7.0%)werepositivefor SARS-CoV-2,including37homelessindividuals(of411,9.0%)and12employees(of152,7.9%). SARS-CoV-2positivitycorrelatedwithsymptoms,although51%ofpatientswhotestedpositivedidnotreport respiratorysymptomsorfever.Amonghomelesspeople,beingyoung(18–34years)(oddsratio3.83,95% confidenceinterval1.47–10.0,p=0.006)andbeinghousedinonespecificshelter(oddsratio9.13,95% confidence interval 4.09–20.37, p < 0.001)were independentfactors associated with SARS-CoV-2 positivity(ratesof11.4%and20.6%,respectively).

Discussion:SymptomscreeningaloneisinsufﬁcienttopreventSARS-CoV-2transmissioninvulnerable shelteredpeople.Systematictestingshouldbepromoted.

Introduction

SinceMarch2020,coronavirusdisease2019(COVID-19),which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread to more than 200 countries and territories worldwide (Johns Hopkins Coronavirus Resource Center, 2020). Homeless people are a vulnerable group who maypotentiallybeexposedtothisinfectionandpotentiallyhave

severeroutcomes thanthe general populationbecauseof their poorliving conditions, higher prevalence of comorbidities, and mentalandphysicalconditionsimpairedbysubstanceoralcohol abuse(Karetal.,2020;Kirby,2020;Limaetal.,2020;Netoetal., 2020; Tsai and Wilson, 2020) Crowded conditions in shelters without speciﬁc preventive measures could facilitate viral transmission(Peate,2020;Woodetal.,2020).Inanearlystudy conductedbetweenMarchandApril2020inHamilton,Canada, COVID-19wasdiagnosedin1%ofshelteredhomelesspeopleand 5%ofstaffmembers(Bodkinetal.,2020).InseveralUScities,inthe sameperiod,1192residentsand313staffmembersweretestedin 19homelessshelters,andhighratesofSARS-CoV-2carriagewere observedinresidents(25%)andstaffmembers(11%)(Baggettetal.,

*Correspondingauthorat:VITROME,InstitutHospitalo-Universitaire

Méditer-ranéeInfection,19–21BoulevardJeanMoulin,13385MarseilleCedex05,France.

E-mailaddress:philippe.gautret@club-internet.fr(P.Gautret).

https://doi.org/10.1016/j.ijid.2021.02.026

(http://creativecommons.org/licenses/by/4.0/).

ContentslistsavailableatScienceDirect

International

Journal

of

Infectious

Diseases

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2020a; Mosites et al., 2020); furthermore, the prevalence was reportedtobe9.7–15.5%amongresidentsand13.3–14.8%among staff members in three homeless shelters in Washington state (Tobolowskyet al.,2020)and67.3%among residentsand16.7% amongstaffmembersinonehomelessshelterinSanFrancisco. (Imbertetal.,2020).Inaddition,2.0%ofresidentsfrom14shelters inWashingtonstatetestedpositive(Rogersetal.,2021),11.9%of residentsfromﬁvessheltersinRhodeIslandtestedpositive(Karb etal.,2020),2.1%ofresidentsfrom24sheltersinAtlantatested positive(Yoonetal.,2020)and33.1%ofshelteredhomelessand marginallyhousedpeopleinBostontestedpositive(Baggettetal., 2020b). This raised concerns that the virus may be widely transmittedwithinhomelessshelters.

Overthepasttwodecades,ourinstitutehasconductedalarge numberofsurveysamonghomelesspeopleintwoshelters(Aand B) in Marseille, France. We observed a high prevalence of respiratorysymptomsandsigns (Badiagaetal.,2009)and high carriageratesofbothrespiratoryviruses(Thibervilleetal.,2014) andbacteria(Lyetal.,2019),suggestingthatSARS-CoV-2infection might also be frequent in this population. On the basis of preliminaryinformationthatsomehomelesspeoplefromthese two shelters exhibited COVID-19 symptoms, we organised a screeningcampaign incollaborationwiththestaffin chargeof these shelters. We subsequently received other requests for screening from several accommodation centres specialising in housingvulnerablepeople.Inthisstudy,wepresenttheresultsof SARS-CoV-2 screening campaigns conducted among sheltered homelessindividuals incomparisonwithasylum-seekers, other peoplelivinginprecariousconditionsandemployeesworkingin the accommodation centres. We also investigated the role of potentialriskfactorsforSARS-CoV-2carriageamongthehomeless population.

Methodsandmaterials Ethics

Ethicalapproval was obtainedfromtheInstitutionalReview BoardandEthicsCommitteeofourinstitute(2020-015). Setting,studydesignandpopulation

Across-sectionalsurveywasconductedbetween26Marchand 17April2020indifferentpopulations,includinghomelesspeople residing infourshelters (A–D)and fourhotels(1–4)that were speciﬁcallyusedtohousehomelesspeopleduringthepandemic, otherpeoplelivinginprecariousconditions(housedinresidences αandβ),asylum-seekers(housedinresidence

g

)andemployees working in these accommodation centres. This represents a convenient sample because theseresidences requestedtesting. Follow-upwasconductedinthreeshelters(A_–C)untilNovember 2020.

Homeless shelters A–C include emergency (overnight stay) unitswitharapidturnover(7_–14nights),andspecial(permanent stay) units dedicated to high-risk sedentary homeless people characterisedbyahighlevelofpoverty,poorhygiene,alcoholism, mentalillnessandchronicdiseases.SheltersAandBareformen only,whileshelterCisforwomenonly.ShelterDhousesmaleand femalehomelesspeopleandoffersthepossibilityforthemtokeep their pets if needed. The characteristics of the facilities are describedinTable1.Allresidentsofhomelessshelterswereplaced understrictlockdownfrom17March(deﬁnedas“C0”),inlinewith thewholeFrenchpopulation,requiringallhomelesspeopletostay intheshelter24hoursaday.Homelesspeoplewererequirednotto leave the shelters for any reason (with rare exceptions). The residencesprovidedallnecessaryitems.A fewindividualswere

T able 1 Chara cte ristics of shelt ers, ho tels and re sidences. Homeless shelt ers and ho tels R esidence for speci ﬁ c populations li ving in pr ecarious conditions R esidence for asy lum-seekers Shelt er A Shelt er B Shelt er C Shelt er D H o tel 1 H o te l 2 H o te l 3 Hot el 4 R esidence α R esidence β R esidence g Descrip tiv e Type of re sidents A dult males A dult males A dult females A dult males and females and pets A dult males A dult males A dult females A dult females A dult males and females (drug addiction, chro nic diseases, etc.) T eenag e mot hers and their childre n Fa mil y gr oups a T o tal capacity/emerg ency beds/long-te rm beds 3 1 0/260 – 280/30 – 50 283/2 48/35 64/50/1 4 3 3 /N A/N A 7 0/N A/N A 1 0 0/N A/ NA 1 5/N A/ NA 1 0/N A/ NA 20/N A/N A 20/N A/N A 50/N A/N A R oom or apartment 3– 8 people/ room 2– 3 people/ ro om 2– 12 people/ room 1 person/r oom 2– 3 people/ room 2– 3 people/ room Single room Single room 1– 2 people/ apartment 1 mot her – child(r en) pair/apartment Fa mil y apartments Bathr oom and toi lets Shar ed Share d Shar ed Pri v a te Shar ed Pri v a te Pri v a te Shared Pri v a te Pri v a te Pri v a te Kitchen Shar ed Share d Shar ed Share d Shar ed Share d Share d Shared Pri v a te Pri v a te Pri v a te Open space Larg e terr ace Larg e te rrace , cultur al hall Larg e terr ace Larg e te rra ce, cultur al hall Larg e terr ace Larg e terr ace N one Larg e te rrace N one Cultur al hall, garde n N one Medical car e and beha viour al health re sources b A v ailable at shelt er A v ailable at shelt er A v ailable at shelt er On demand On demand On demand On demand On demand On demand On demand On demand Loc kdown Time betw een ﬁ rst da y o f loc kdow n and scr eening (day s) 1 4 9 1 5 3 1 17 2 0 1 41 42 4 2 8 1 7 N A , n o t applicable. a Single indi viduals wer e housed on the basis of tw o indi viduals per apartment. b “On demand ”: health car e wor kers (nurses and medical doct ors) fr om shelt er B, shelt er C o r SOS medical gr oup can be re q uest ed when necessary .

T.D.A.Ly,N.N.Nguyen,V.T.Hoangetal. InternationalJournalofInfectiousDiseases105(2021)1–6

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newlyadmittedandallweretestedforSARS-CoV-2andisolated beforetheresultswereavailable.Thepopulation(male)ofshelter A(initialgroupA)wassubdividedintothreegroupsbythestaffof thefacilitytoavoidovercrowding:(i)elderlypeople,thosewith reduced mobility and thoseneeding medical carewerekeptin shelterA;(ii)peopleaged18–45yearswereprogressivelymoved tohotel1fromC0toC7;(iii)peopleaged30–80yearsweremoved tohotel2 fromC7toC14.Similarly, thepopulation(female)of shelterC (initialgroupC)wassubdividedintothreegroups:(i) elderly people,thosewith reducedmobility and those needing medicalcarewerekeptinshelterC;(ii)pregnantwomenandthose with mental illness were moved to hotel 3 at C0; (iii) other residentswere movedtohotel 4 at C0.Allresidents movedto hotelswerekeptunderrelativelystrictlockdownfromC0,withthe exceptionofthedayoftransfer.

Residenceαisdedicatedtoindividualscharacterisedbyahigh level of poverty, poor hygiene, alcoholism, mental illness and chronicdiseases,includingdrugaddiction.Residenceβspecialises in housingteenage mothers and theirchildren. Residence

g

is dedicatedtoasylum-seekers,includingfamilygroupsandsingle individuals.Allthreeresidencesofferlong-termhousing,andall residentswerekeptunderstrictlockdownfromC0.

TheseresidenceswerelocatedindifferentpartofMarseille,far fromeachother.

Employeesofthedifferentfacilitiesworkingindifferentsectors (managementstaff,socialworkers,nurses,cleaningstaff,catering staffandsecuritystaff)returnedtotheirhomesonadailybasis afterﬁnishingwork.Employeesdidnotworkinmultiplefacilities, withtheexceptionofmedicalstaffinsheltersAandC,whocared forpeopleinhotels1and2andinhotels3and4,respectively. ScreeningforCOVID-19

Participantswereencouragedbythemanagementstaffofthe facilitiestobetestedandwerethenrecruitedonavoluntarybasis.

They were systematically asked to provide basic demographic information (sex, age and country of origin), information on chronicconditionsandinformationonanyrespiratorysymptoms orfeverinthe2weeksbeforesampling.Bodytemperaturewas measuredwitha foreheadinfraredthermometer.Wedeﬁned a feverasameasuredtemperatureof37.8Corhigher.Nasalsamples weresystematicallycollectedontransport mediumwithuseof SigmaTranswabs(MedicalWire,Corsham,UK).Forself-sampling, participantswere invited toinsert the swab intotheir nostrils (about2cm).Ifindividualswereunabletoperformself-sampling, trainedinvestigatorsdidthesampling.Specimenswere immedi-atelyprocessed for SARS-CoV-2 PCRtesting. Homelesspeoples_’ petswerealsotestedwiththeapprovaloftheirowner,andtheir nasalswabswerecollectedbyvets. Theparticipantsormedical staffwereinformedofthetestresultwithadelayof24h.Before testing,residentsweretoldwhatwouldhappenifthetestresult waspositive.Residentswhotestedpositiveweremovedtospecial facilitiesforCOVID-19homelesspatientisolationorkeptinasingle room at residences with strict isolation measuresfor 14 days. Infectedstaffmemberswereinstructedtostayathomefor14days. PCRassay

Real-timereversetranscriptionPCRampliﬁcationwasusedto conﬁrmthepresenceofSARS-CoV-2RNAtargetingthegenecoding fortheenvelope(E)protein,aspreviouslydescribed(Amraneetal., 2020).Resultswereconsideredpositivewhenthecyclethreshold (Ct)valueofreal-timePCRwas35orless.

Statisticalanalysis

StatisticalanalyseswereperformedwithSTATA11.1(StataCorp. LLC,CollegeStation,TX,USA).Percentagedifferencesweretested withPearson’schi-squaretestorFisher’sexacttestasappropriate. MeansofquantitativedatawerecomparedwithStudent'sttest.A

Table2

Numbersofindividualsscreenedandresultsofsevereacuterespiratorysyndromecoronavirus2(SARS-CoV-2)PCRdetectionaccordingtohousingstructures.

Greycellscorrespondtothefourgroupsinstudy,homelesspeople(N=411),otherspeciﬁcpopulationslivinginprecariousconditions(N=58),asylum-seekers(N=77)and

employees(N=152),andtheSARS-CoV-2prevalenceineachgroup.

NA,notapplicable.

1

Acceptancerate.

2

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pvalueless than0.05 wasconsideredstatisticallysignificant. A separate multivariate logistical regression analysiswas usedto identifyindependentriskfactorsforSARS-CoV-2carriage preva-lenceamongallindividualsandinselectedgroups(whenpositive caseswerefound).Theresultsarepresentedaspercentagesand oddratios(ORs)withthe95%confidenceinterval(CI).Theinitial model includedvariableswithp<0.2.Thestepwiseregression procedureandlikelihood-ratiotestswereappliedtodeterminethe finalmodel.

Results

Participantcharacteristics

Overall,885individualswerepresentinthevariousfacilitiesat thetimeofenrolment,including716residentsand169employees (Table2).Atotalof698individuals(78.9%) agreedtobetested, including411homelesspeople(58.9%),58non-homelesspeople livinginprecariousconditions(8.3%),77asylum-seekers(11.0%), and 152employees (21.8%).Overall,38.7%wereenrolled before C14,45.9% betweenC14and C20and 15.4%atC21 orlater.The overallacceptancerateforSARS-CoV-2testingvariedsigniﬁcantly accordingtothehousingfacility,rangingfrom41.7%to91.7%.The overallacceptancerateamonghomelessindividualswas74.6%and was signiﬁcantlylower than that of employees workingin the homelesscentres(88.7%,p0.001)(Table2).Theacceptancerate amongpeoplehousedinotherfacilitiesrangedfrom75.5%to100% andtendedtobelowerthanthatofemployeesinthesefacilities (Table2).

The socio-demographic characteristics of the different pop-ulationsarepresentedinTable3.Themale-to-femaleratiowas3:1 andthemedianagewas35.0years(rangefrom0to91years),with signiﬁcant variations among different populations. A male predominance was observed among homeless people and asy-lum-seekers.Childrenaged15yearsoryoungeraccountedfor7.5% of all residents. Two-thirds of individuals were migrants. A predominance of African origin was found among homeless

individuals, while other people living in precarious conditions andemployees weremorelikelytobeEuropean.Most asylum-seekershadAfricanorAsianorigin.Therewereonlyfourpregnant women(between26and36weeksofpregnancy),allhousedin hotel3.

ClinicalsymptomsandSARS-CoV-2detection

Among all the participants, 22.1% reported at least one respiratorysymptomorfever,withsigniﬁcantvariationsamong differentpopulations.Thehighestprevalencewasobservedamong employees(25.7%)andhomelesspeople(24.3%).Acoughwasthe mostcommonlyreportedsymptom(32.7%),followedby rhinor-rhoea(20.4%),dyspnoea(12.2%)andfever(12.2%).Nodeathswere reportedduringthestudyperiod.

Intotal,49participants(7.0%)testedpositiveforSARS-CoV-2, including37homelesspeople(of441,9.0%)and12employees(of 152,7.9%,includingsevensecuritystafffromsheltersA,BandC andresidence

g

,fournursesfromshelterBandonemanagement staffmemberfromshelterC).Onlytwofemalehomelesspeople testedpositive,includingonewomanwhowas36weeks’pregnant andwhofrequentlyattendedthehospitalduringthelockdownand onepersonwithmentalillnesslivingathotel3whodidnotcomply withlockdownmeasures,frequentlyleavingthehotel.

Twodogsbelongingtotwodifferenthomelesspeopleinshelter Dtestednegative.Withregardtothehousingfacilities,thehighest SARS-CoV-2positivityrateswereobservedinhomelesspeoplein hotel1(39.1%),inshelterA(18.5%)andinhotel2(14.3%).Among employees,thehighestpositivityrateswereinthoseworkingat homelessshelterB(14%)andhomelessshelterA(12.5%).

Of the 49 SARS-CoV-2-positive participants, 51.0% were asymptomatic.Participantswhotestedpositiveweremorelikely to be symptomatic compared with participants who tested negative (OR 3.8, 95% CI 2.1–6.9, p < 0.001). There was no signiﬁcant difference in PCR Ct values between asymptomatic individuals(meanCt26.9,standarddeviation5.0)and symptom-aticindividuals(Ct25.75.4,p=0.43).Theoverallproportionof

Table3

Characteristicsofdifferentpopulationsstudied.

Characteristic Totalscreened

(N=698) Homelesspeople (N=411) Otherspeciﬁc populationsin precarious conditions(N=58) Asylumseekers (N=77) Employees (N=152) pd

Timeofscreening BeforeC14,n(%)e

270(38.7) 227(55.2) 0(0) 0(0) 43(28.3) <0.001 FromC14toC20,n(%) 320(45.9) 159(38.7) 0(0) 77(100) 84(55.3) AtC21andafter,n(%) 108(15.4) 25(6.1) 58(100) 0(0) 25(16.4) Sexa Male,n(%) 529(75.8) 369(89.8) 25(43.1) 50(64.9) 85(55.9) <0.001 Female,n(%) 169(24.2) 42(10.2) 33(56.9) 27(35.1) 67(44.1)

Age(years) Range(min–max) 0–91 18–91 0–86 0–67 21–77

MeanSD 37.416.9 40.415.6 25.024.0 21.613.6 41.911.1 <0.001

Median,interquartilerange 35.0,26–49 37.0,28–52 19.0,2–49 24.0,10–31 41.5,33–50

Children15years,n(%)b 41(7.5) 0(0) 19(32.8) 22(28.6) NA <0.001 Birthplace Europe,n(%) 267(38.3) 99(24.1) 45(77.6) 12(15.6) 111(73.0) <0.001 Africa,n(%) 351(50.3) 269(65.5) 11(19.0) 32(41.6) 39(25.7) Asia,n(%) 80(11.5) 43(10.5) 2(3.4) 33(42.9) 2(1.3) Pregnantwomenn/N(%)c _4/150_(2.7) _4/42_(9.5) _0/25₍₀₎ _0/16₍₀₎ _0/67₍₀₎ _0.002 Presenceof respiratory symptomand fever

Atleastonesymptom,n(%) 154(22.1) 100(24.3) 10(17.2) 5(6.5) 39(25.7) 0.003

Cough,n(%) 85(12.2) 55(13.4) 7(12.1) 1(1.3) 22(14.5) 0.02

Rhinorrhoea,n(%) 64(9.2) 49(11.9) 1(1.7) 0(0) 14(9.2) 0.002

Dyspnoea,n(%) 42(6.0) 27(6.6) 2(3.4) 2(2.6) 11(7.2) 0.41

Sorethroat,n(%) 37(5.3) 23(5.6) 2(3.4) 0(0) 12(7.9) 0.08

Fever,n(%) 19(2.7) 10(2.4) 1(1.7) 2(2.6) 6(3.9) 0.75

NA,notapplicable;SD,standarddeviation.

a

Numberofindividualsforwhomdatawereavailable.

b

Of546residents.

c

Of150femalesaged15yearsorolder.

d

Comparisonamongthefourgroups.

e

C14referstoday14oflockdown.

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asymptomaticcarriersamongallindividualstestedwas3.6%and thatofsymptomaticcarrierswas3.4%.

Table 3 shows SARS-CoV-2positivity rates among homeless people according to the time of screening, demographics and housing facility obtained by univariate analysis. No significant differenceswereobservedaccordingtosexandcountryoforigin regardingSARS-CoV-2positivityrates.ScreeningbetweenC14and C20andscreeninginthegroupApopulation(shelterAandhotels to which people from shelter A were moved) resulted in a significantlyhigherproportionofparticipantswithpositivePCR testresultsascomparedwithscreeningbeforeC14orscreeningin otherhomelessfacilities.Inaddition,beingyoung(18_–34years) was associatedwith anincreased likelihood of virusdetection. Cough, rhinorrhoeaand feverwereassociatedwithSARS-CoV-2 carriage. Frommultivariate analysis(Table 4), beingyoung (OR 3.83,95%CI1.47–10.0,p=0.006)andscreeningconductedinthe group A population (OR 9.13, 95% CI 4.09–20.37, p < 0.001) remainedsignificantlyassociatedwithahigherlikelihoodof SARS-CoV-2detection.

Measurestomitigatetheriskoftransmissionandfollow-up Measurestomitigatetheriskoftransmissionincludedstaying inthehousingfacility,avoidinggatheringsofpeople(includingby moving individuals from shelters to hotels), wearing a mask, keepingdistancefromothers,washinghandswithsoapandwater frequentlyandforatleast20seconds,practisingcoughetiquette, and avoidingtouchingtheeyes,noseormouth withunwashed hands. Follow-upconductedinsheltersA,BandCresultedin a strongdecreaseofPCRpositivityrates,with1.1%ofresidentsof shelter A and 0.4% residents of shelter B testing positive in SeptemberandNovember,respectivelywhilenoresidentofshelter CtestedpositiveinOctober(Figure1).

Discussion

Toourknowledge,thisistheonlystudyaddressingSARS-CoV-2 carriageamongdifferentprecariouspopulationsincluding home-lessadultsbutalsochildrenandotherhard-to-reachpopulations duringtheCOVID-19outbreakinFrance.InMarseille,theﬁrstcase ofCOVID-19inthegeneralpopulationwasdiagnosedon3March 2020,andtheepidemicpeakedduringtheﬁrstweekofApriland remainedactiveuntiltheendofApril( https://www.mediterranee-infection.com/covid-19/). The strength of our study is its large

populationsize,withahighacceptancerate (78.9%)fortesting, particularly among individuals living in precarious conditions (92.1%), suggesting thatthis populationis concernedabout the disease.

WefoundanoverallSARS-CoV-2positivityrateof7.0%,with mostinfectedindividualsamonghomelesspeopleandemployees working in homeless facilities, while no cases were found in asylum-seekers and in other people also living in precarious conditions.Detectionof SARS-CoV-2correlatedwithsymptoms, althoughmany patientswho testedpositive didnotreportany respiratorysymptomsorfeveratthetimeofsampling.Itcannotbe excludedthatsomeofthemwereactuallypresymptomatic.The high rate of asymptomatic SARS-CoV-2 carriers is in line with studiesconductedinhomelesssheltersintheUSA(Baggettetal., 2020a;Karbetal.,2020;Rogersetal.,2021).Asymptomaticand presymptomatictransmissionmaythereforebethepredominant SARS-CoV-2 transmission mode in shelters. As a consequence, symptom-guided screening in this setting is not an effective strategy.Giventhathomelesspeopleandprofessionalsincontact with homeless people are at a high risk of COVID-19, these populationsshouldbeneﬁtfromscreeningcampaigns,andspeciﬁc measures aimedat mitigating the risks of transmission of the disease, including personal protective measures, within these populationsandtotheoverallpopulationshouldbeimplemented. Amongthepopulationsofthefourhomelessshelters(A–D)that were screened, the highest prevalence was observed in the populationinitiallyhousedinshelterA. Thismayhaveresulted fromthehighernumberofindividualsperroominthisshelter,as comparedwiththeothershelters,which mayhaveencouraged transmissionofthevirus.Sleepinginshareddormitoriesanduseof sharedbathrooms,toiletsandkitchensmaketheimplementation ofsocialdistancingmeasuresinthecontextofhomelessshelters particularly challenging. Being young (18–34 years) was an independentfactorassociatedwithSARS-CoV-2detectioninthe homeless group,which may bedue to a higher propensityfor youngerhomelesspeopletodevelopsocialinteractionswithinthe sheltersandhotelsascomparedwithpeopleaged50yearsorolder. Measuresthatwereundertaken byshelterstaffmembersto mitigatetheriskof transmissionwereeffectiveinreducing the numbersofcasesamongresidents,withonlyaslightincreasein the number of cases observed in shelter B during the second epidemicinMarseille.

Thisworkhassomelimitations.Ourstudypopulationwasnot randomly and homogenously recruited. Participants’ medical

Table4

Associationsbetweenmultiplefactorsandsevereacuterespiratorysyndromecoronavirus2(SARS-CoV-2)positivityamong411homelesspeople(univariateandmultivariate

analysis).

Characteristic Positive(N=37) Negative(N=374) Univariate Multivariate

OR(95%CI) p aOR(95%CI) p

Timeofscreening BeforeC14,n(%)b

9(4.0) 218(96.0) Reference

FromC14toC20,n(%) 28(17.6) 131(82.4) 5.17(2.36–11.31) <0.001

AtC21andlater,n(%) 0(0) 25(100) NA 0.6

Sex Male,n(%) 35(9.5) 334(90.5) Reference

Female,n(%) 2(4.7) 40(95.2) 1.56(0.48–9.04) 0.32

Age(years) 50 7(6.2) 105(93.8) Reference Reference

35–49 9(8.3) 100(91.7) 1.34(0.48–3.76) 0.56

18–34 20(11.4) 156(88.6) 1.92(0.78–4.7) 0.15 3.83(1.47–10.0) 0.006

Birthplace Europe,n(%) 6(6.0) 93(94.0) Reference

Africa,n(%) 27(10.0) 242(90.0) 1.72(0.69–4.32) 0.24

Asia,n(%) 4(9.3) 39(90.7) 1.58(0.42–5.94) 0.49

Housingfacilitya _Other_homeless_facilities,_n_(%) ₁₁_(3.9) ₂₇₄_(96.1) _Reference _Reference

GroupA,n(%) 26(20.6) 100(79.4) 6.47(3.1–13.6) <0.001 9.13(4.09–20.37) <0.001

aOR,adjustedoddsratio;CI,conﬁdenceinterval;NA,notapplicable;OR,oddsratio.

Boldindicatesthevariablesusedininitialmultivariatemode.

a

GroupAincludesshelterAandhotels1and2.OtherhomelessfacilitiesincludesheltersB,CandDandhotels3and4.

b

(7)

histories and use of individual preventive measures were not documented. Individuals were not asked about anosmia and ageusia. No informationwas available regarding possible inter-actionsofpopulationsatotherfacilities(soupkitchensandday shelters)beforelockdown.Notwithstandingtheselimitations,our dataprovidenovelinsight intotheepidemiologyofSARS-CoV-2 among differentvulnerable urbanpopulations. The surveyalso revealstheroleofsharedhousinginrelationtoviraltransmission withinaccommodationcentres.

Funding

ThisworkwassupportedbytheFrenchGovernmentunderthe “InvestmentsfortheFuture”programmemanagedbytheNational Agencyfor Research(ANR),Méditerranée-Infection10-IAHU-03, and was also supportedby RégionProvence-Alpes-Côte d’Azur. This workreceived _ﬁnancialsupport fromtheFondation Médi-terranéeInfection.

Acknowledgements

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Figure1.Positivityrates(%)ofsevereacuterespiratorysyndromecoronavirus2

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