brazjinfectdis2020;24(3):261–263
w w w . e l s e v i e r . c o m / l o c a t e / b j i d
The
Brazilian
Journal
of
INFECTIOUS
DISEASES
Brief
communication
Will
environmental
changes
in
temperature
affect
the
course
of
COVID-19?
Carlos
Del
Rio
a,
Adrián
Camacho-Ortiz
b,∗aEmoryUniversitySchoolofMedicine,DepartmentofInternalMedicine,DivisionofInfectiousDiseases,Atlanta,GA,UnitedStates bHospitalUniversitario“Dr.JoséEleuterioGonzález”,DepartmentofHospitalEpidemiology,MonterreyN.L.,Mexico
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Articlehistory:
Received23March2020 Accepted17April2020 Availableonline4May2020
Keywords:
Coronavirus COVID-19 Temperature
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Whiletheoutbreakhasreachedeveryregionoftheworld,itisundeniablethatcountriesin thesouthernhemisphereseemtobelessaffected,wherecaseshavebeenreported,these havebeenimportedandtravelrelated.Weanalyzedtheclimatetemperaturefromvarious regionsaccordingtotheircurrentongoinghuman-to-humantransmissionstatus.We stud-ied3groups;Group1,10provincesfromChinawithmajorityofCOVID-19cases;Group2, areaswherecontinuoushorizontaltransmissionoutsideofChinahadbeenreported;and group3,areaswhereimportedcaseshadbeendetectedandnohorizontaltransmissionhad beendocumentedafteratleastsevendayssincethefirstcasewasreported.Theregions withoutongoinghuman-to-humantransmissionshowedsignificantlyhighertemperatures whencomparedtoChinaandcountrieswithongoinghuman-to-humantransmission,with overan11-degreedifference.Theaveragerainfallduringthestudyperiodwassignificantly higherinthoseregionswithoutOHHTwhencomparedtotheChineseprovinceswith ongo-inghuman-to-humantransmissionandtheregionswithactivetransmissionofSARS-CoV-2. Ourfindingsshowstatisticallysignificantdifferencesbetweenregionswithongoing human-to-humantransmissionofCOVID-19casescomparedtothoseregionswithouthorizontal transmission.Thisphenomenoncouldhaveimplicationsinthebehavioroftheongoing COVID-19outbreakinthefollowingmonths.
©2020SociedadeBrasileiradeInfectologia.PublishedbyElsevierEspa ˜na,S.L.U.Thisis anopenaccessarticleundertheCCBY-NC-NDlicense(http://creativecommons.org/ licenses/by-nc-nd/4.0/).
Currently more than 60 countries have been affected and almost 100,000 cases worldwide have been reported since thebeginningofthenovelcoronavirusinfection(COVID-19) outbreak.1 SARS-CoV-2(taxonomic nameofthevirus
caus-ingCOVID-19)hasshowndiversediseaseseverity,ragingfrom asymptomatictoacuterespiratorydiseasesyndromewitha 1.4–2.3%mortalityrate.2,3
∗ Correspondingauthor.
E-mailaddress:[email protected](A.Camacho-Ortiz).
Whiletheoutbreakhasreachedeveryregionoftheworld exceptAntarctica,itisundeniablethatcountriesinthe south-ern hemisphere seem to be less affected, and were there havebeen casesreportedthemajorityhavebeen imported andtravelrelated.1Therehasbeenspeculationthatas
tem-peraturesincreasewithSpringandSummerintheNorthern Hemispheretherewillbeanassociateddeclineinthenumber
https://doi.org/10.1016/j.bjid.2020.04.007
1413-8670/©2020SociedadeBrasileiradeInfectologia.PublishedbyElsevierEspa ˜na,S.L.U.ThisisanopenaccessarticleundertheCC BY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).
262
braz j infect dis.2020;24(3):261–263Table1–Comparisonoftemperatureandrainfallamongthedifferentregions.
Provincesfrom China Regionswith ongoinghuman tohuman transmission
PvsChina Regionswithout ongoinghuman
tohuman transmission
PvsChina
Meanhightemperature(◦C) 14.66(±7.92) 9.42(±4.17) 0.002 20.50(±11.68) 0.0001 Meanlowtemperature(◦C) 4.52(±8.90) 0.86(±4.06) 0.002 13.62((±11.19) 0.001 Averagetemperature(◦C) 8.74(±9.52) 5.14(±5.94) 0.001 17.06(±11.94) 0.0009 Averagerainfall(mm) 20.62(±20.70) 74.29(±44.38) 0.003 117.82(±117.04) 0.009
ofcases.Iftrue,thisgiveshopetotheregionswhereSpringis startingsoon,butalsoshouldcauseconcerninthesouthern hemispherewereAutumnistobegin.
Wesoughttoanalyzetheclimatetemperaturefromvarious regionsaccordingtotheircurrentongoinghuman-to-human transmission(OHHT)status.Westudied3groups;Group1,10 provincesfromChinawithmajorityofCOVID-19casessince December31,2019throughFebruary 29,2020(92.2%ofthe totalcasesinChina):Hubei,Guangdong,Henan,Hunan, Shan-dong,Jiangsu, Sichuan,Hebei, Zhejiang,and Anhui.Group 2,areas where continuoushorizontal transmissionoutside ofChina had been reported: Italy (Lombardo and Veneto), SouthKorea(Daegu,Gyeongbuk,Gyeonggi),andIran(Theran Qom,Gilan); andgroup3, areaswhereimportedcaseshad been detected and no horizontal transmission had been documented after at least seven days since the first case was reported:Philippines (Tagbilaranand Manila), Belgium (Brussels),Findland(Rovaniemi),Egypt(Cairo),andAustralia (Melburne,SidneyandBrisbane).
Daily registered maximum and minimal ambient tem-peratureswereobtainedfromtheWeatherChannelwebsite (https://weather.com/)from all studiedregions, using their biggest metropolitan area as reference. For comparison of meanmaximumandminimumtemperaturesStudentTtest orMann–WhitneyUtestwereperformed.
The regions without OHHT showed significantly higher temperatureswhencompared toChinaandcountries with OHHT,withovera1◦Cdifference.TheregionswithOHHThad thelowesttemperaturessuchasChinaandotherregionsof group2.For countrieswithoutOHHTtheaverage tempera-turewas8.32◦Chighercomparedtotheothergroups(Table1). Theaveragerainfallduringthestudyperiodwassignificantly higherinthoseregionswithoutOHHTwhencomparedtothe ChineseprovinceswithOHHT(>97.2mmmorerainfall)and theregionswithactivetransmissionofSARS-CoV-2(>43.5mm morerainfall).
Ithasbeendescribedthattemperaturesand environmen-talfactorscontributetothesurvivalofdifferentcoronavirus.4
Studieshavefoundthatlowtemperaturesanddryconditions favor MERS-CoV survival and dissemination; nevertheless, Altamimi et al.5 found that high temperatures, coupled
withhigh ultraviolet index, low windspeeds, and low rel-ative humidity were contributors to increased MERS-CoV cases.
Slightdifferencesintemperaturehaveasignificantimpact onMERSCoVandSARSCoVsurvivalintheenvironment.Otter et al.6 compiled various studies addressingthe survivalof
respiratoryvirusesonsurfacesandshowedthatslight differ-encesintemperatureandrelativehumidityreduceorenhance
viability;someofthesevariationsweresimilartothosefound inouranalysis.
Althoughtemperatureandhumiditychangesinthe envi-ronmentcanpotentiallyaffectthebehaviorofSARS-CoV-2in acommunity.Thesearefactorsthatcanbeeasilyadjustedin thehospitalsetting,sothatsomeoftheextremesin temper-atureandrelativehumiditymaynotapplyinthehospital.
To further complicate the analysis, environmental cli-matechangesmaynotfavorrespiratoryviruspandemicsas expected,theinitialcasesofinfluenzaAH1N12009startedat theendoftheregularinfluenzaseasoninMexico(March–April 2009) andwentontohaveanenormousimpactduringthe followingsummermonths.7
Ourselectioncriteriafortheregionstriedtocompensate thevariationsthatmanycountrieshaveindetectionpractices and resourcesforthis purposeaswellasthe possibilityof underreportingthatmaylimittheextentourfindings.In con-clusion,therewerestatisticallysignificantdifferencesamong regions with OHHT of COVID-19 cases compared to those regionswithouthorizontaltransmission.Thisphenomenon couldhaveimplicationsinthebehavioroftheongoing COVID-19outbreakinthefollowingmonths.
Conflicts
of
interest
Theauthorsdeclarenoconflictsofinterest.
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1.Coronavirusdisease2019(COVID-19)situationreport–43:
https://www.who.int/docs/default-source/coronaviruse/ situation-reports/20200303-sitrep-43-covid-19.pdf?sfvrsn= 2c21c09c2[lastaccessed03.03.20].
2.WuZ,McGooganJM.Characteristicsofandimportantlessons fromthecoronavirusdisease2019(COVID-19)outbreakin China:summaryofareportof72314casesfromtheChinese CenterforDiseaseControlandPrevention.JAMA.2020,
http://dx.doi.org/10.1001/jama.2020.2648.PublishedFebruary 24.
3.GuanWJ,NiZY,HuY,etal.Clinicalcharacteristicsof coronavirusdisease2019inChina.NEnglJMed.2020,
http://dx.doi.org/10.1056/NEJMoa2002032[publishedonline aheadofprint,28.02.20].
4.GardnerEG,KeltonD,PoljakZ,VanKerkhoveM,von DobschuetzS,GreerAL.Acase-crossoveranalysisofthe impactofweatheronprimarycasesofMiddleEastrespiratory syndrome.BMCInfectDis.2019;19:113.Published04.02.19.
5.AltamimiA,AhmedAE.Climatefactorsandincidenceof MiddleEastrespiratorysyndromecoronavirus.JInfectPublic Health.2019,http://dx.doi.org/10.1016/j.jiph.2019.11.011.
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6.OtterJA,DonskeyC,YezliS,DouthwaiteS,GoldenbergSD, WeberDJ.TransmissionofSARSandMERScoronavirusesand influenzavirusinhealthcaresettings:thepossibleroleofdry surfacecontamination.JHospInfect.2016;92:235–50.
7.Perez-PadillaR,delaRosa-ZamboniD,PoncedeLeonS,etal. Pneumoniaandrespiratoryfailurefromswine-origininfluenza A(H1N1)inMexico.NEnglJMed.2009;361:680–9.
