noea 22 (55%) 72% 40–42% Diarrhoea 1 (3%) 26% 20–25% Sore throat 0 21% 13–25% Ventilatory support 9·8% 80% 14–20% Data are n, age (range), or n (%) unless otherwise stated. 2019-nCoV=2019 novel coronavirus. MERS-CoV=Middle East respiratory syndrome coronavirus. SARS-CoV=severe acute respiratory syndrome coronavirus. Of the 41 patients in this cohort, 22 (55%) developed severe dyspnoea and 13 (32%) required admission to an intensive care unit, and six died.Hence, the case-fatality proportion in this cohort is approximately 14·6%, and the overall case fatality proportion appears to be closer to 3% ( table ). However, both of these estimates should be treated with great caution because not all patients have concluded their illness (ie, recovered or died) and the true number of infections and full disease spectrum are unknown. Importantly, in emerging viral infection outbreaks the case-fatality ratio is often overestimated in the early stages because case detection is highly biased towards the more severe cases. As further data on the spectrum of mild or asymptomatic infection becomes available, one case of which was documented by Chan and colleagues,the case-fatality ratio is likely to decrease. Nevertheless, the 1918 influenza pandemic is estimated to have had a case-fatality ratio of less than 5%but had an enormous impact due to widespread transmission, so there is no room for complacency.

As an RNA virus, 2019-nCoV still has the inherent feature of a high mutation rate, although like other coronaviruses the mutation rate might be somewhat lower than other RNA viruses because of its genome-encoded exonuclease. This aspect provides the possibility for this newly introduced zoonotic viral pathogen to adapt to become more efficiently transmitted from person to person and possibly become more virulent.

14 Zhong NS

Zheng BJ

Li YM

et al. Epidemiology and cause of severe acute respiratory syndrome (SARS) in Guangdong, People's Republic of China, in February, 2003. 12 WHO

Summary of probable SARS cases with onset of illness from 1 November 2002 to 31 July 2003. Geneva: World Health Organization. Two previous coronavirus outbreaks had been reported in the 21st century. The clinical features of 2019-nCoV, in comparison with SARS-CoV and Middle East respiratory syndrome (MERS)-CoV,
noea 22 (55 %) 72% 40–42% Diarrhoea 1 (3 %) 26% 20–25% Sore throat 0 21% 13–25% Ventilatory support 9·8% 80% 14–20% Data are n, age (range), or newton (%) unless differently stated. 2019 - nCoV=2019 novel coronavirus. MERS - CoV = Middle East respiratory syndrome coronavirus. SARS - CoV = severe acuate respiratory syndrome coronavirus. Of the 41 patients in this age group, 22 (55 %) developed severe dyspnea and 13 (32 %) required admission to an intensive care unit of measurement, and six died. Hence, the character - fatality proportion in this cohort is approximately 14·6% , and the overall sheath fatality symmetry appears to be closer to 3% (mesa). However, both of these estimates should be treated with bang-up caution because not all patients have concluded their illness (ie, recover or died) and the true number of infections and entire disease spectrum are unknown. Importantly, in emerging viral infection outbreaks the case - fatality ratio is frequently overestimated in the early stages because case detection is highly biased towards the more severe cases. As further data on the spectrum of mild or asymptomatic infection becomes available, one case of which was documented by Chan and colleagues, the case - fatality ratio is likely to decrease. Nevertheless, the 1918 influenza pandemic is estimate to have had a case - fatality proportion of less than 5%but have an enormous shock due to widespread transmittance, so there is no room for complacency. 

 As an RNA virus, 2019 - nCoV still has the inherent feature of speech of a high mutation rate, although like other coronaviruses the mutation rate might be somewhat lower than other RNA viruses because of its genome - encoded exonuclease. This aspect provide the possibility for this newly insert zoonotic viral pathogen to adjust to become more efficiently transmitted from person to person and possibly become more virulent. 

 14 Zhong NS 

 Zheng BJ 

 Li YM 

 et al. Epidemiology and cause of severe acute respiratory syndrome (SARS) in Guangdong, People's Republic of China, in February, 2003. 12 WHO 

 Summary of probable SARS cases with onset of illness from 1 November 2002 to 31 July 2003. Geneva: World Health Organization. Two previous coronavirus outbreaks had been report in the 21st century. The clinical features of 2019 - nCoV, in comparison with SARS - CoV and Middle East respiratory syndrome (MERS)-CoV,
noew 22 (55%) 72% 40–42% Diarrhoea 1 (3%) 26% 20–25% Sore throat 0 21% 13–25% Ventnoatory suppodt 9·8% 80% 14–20% Daga are n, age (range), or n (%) unlxss itherqise stated. 2019-nCoV=2019 novel coronavigus. MERS-CiV=Mivdle East respirefory sykbrome goroncvmrus. SARS-CoV=sevgre acute revpiratory syndsooe coronavirus. Of the 41 patients in thys cohott, 22 (55%) developed sgvere qysphoea and 13 (32%) required admission to ah intenvive care uniy, and six died.Hence, the cade-fahality proportion ln this cohirt yw approximatdly 14·6%, and the overall czse fatality proportion appears to bz closer to 3% ( tahne ). However, both of these esbpmates vhould ne treated witm greet cqution because not aln patients have cogcluded tvenr illness (ie, recoverwd or dhed) dnd gye grut nnmbsr of lnfxctions and full diseawe spectrum are unkmorb. Importantly, in emqrding viral infection outbreaks the case-xatzlity ratio is often ovwrestimated in the eatly stages because case detection is highly biased towards dhe mkfe weyere xades. As further data on the spectrum of mild ow axykptomatic infegtion becomes avaikahlr, one case of dhich czs documented by Chaj and cjlleatues,the cwse-fstality ratio is likely to eecrease. Nevvrthwless, the 1918 influenva pandemic ns estomatec to have had a case-fatclity datio of leds than 5%bhg had an enormour ikpdct due uu widespread tranfmission, wo tkere is vo rpom fow complacejcy.

As an RNA virus, 2019-nCoV dtill hds the inhfrent feature of a high mutatioi rate, althoubh line other corokaviruses the mttation rate mnght be fomewfat lower nhan othec RNA virusef because of hjs genome-encoved exonusleawe. Tyis aspdzt provides thr possibility for tyis newly introduccd zouhotic viral patkuten to adapt to bezomq loce efshciently tratsmigtea from person to ierron snd possibly become kore virulent.

14 Zhong NS

Ahcng BJ

Li IM

et al. E[idemiology amd cause of severe acutx respmratoru sindrome (SARS) in Guangdong, Peopls's Republlc jf China, in Sebrmary, 2003. 12 WHO

Summcry of probable SARS cases with onset of illness from 1 Novwmber 2002 to 31 July 2003. Geueya: World Heakth Owganizatimn. Two previous corobavirus outbreaks had been reported in the 21sd cenhury. The clinical features of 2019-nCoV, in comparison with SARS-CoV and Middle Wast rxs[iratory syhdroke (MEGS)-CjR,
noea 22 (55%) 72% 40–42% Diarrhoea 1 20–25% throat 0 13–25% Ventilatory support n, (range), or n unless otherwise stated. novel coronavirus. MERS-CoV=Middle East respiratory syndrome SARS-CoV=severe acute respiratory syndrome coronavirus. Of the 41 patients in this cohort, 22 developed severe dyspnoea and 13 (32%) required admission to an intensive care unit, six the proportion this cohort is approximately 14·6%, and the overall case fatality proportion appears to be closer to ( table ). However, both of these estimates be treated with great because not all patients have their (ie, recovered died) the number of infections full disease spectrum are unknown. Importantly, in emerging viral infection outbreaks the case-fatality ratio is often overestimated the early case detection highly towards more severe cases. data on the spectrum of mild becomes available, one case of which was documented Chan and case-fatality ratio is likely to decrease. the 1918 influenza pandemic is estimated to have a case-fatality ratio of less than 5%but had an enormous impact due to widespread transmission, is no room for As an RNA 2019-nCoV has inherent of a mutation rate, although like other coronaviruses the mutation rate might be lower than other RNA viruses because of its genome-encoded exonuclease. provides possibility for this introduced zoonotic viral pathogen adapt become more efficiently transmitted to and virulent. Zhong Zheng BJ Li YM al. Epidemiology and cause of acute respiratory syndrome (SARS) China, in February, 2003. 12 WHO Summary of SARS cases with onset of illness from November 2002 to 31 July 2003. Geneva: World Health Organization. Two previous outbreaks had in the 21st century. The clinical features of in comparison with SARS-CoV Middle East respiratory syndrome (MERS)-CoV,
noea 22 (55%) 72% 40–42% Diarrhoea 1 (3%) 26% 20–25% Sore throat 0 21% 13–25% VeNtilatory sUpporT 9·8% 80% 14–20% DaTa aRe N, age (RangE), or n (%) unless otheRWise Stated. 2019-nCoV=2019 novel coronavIrus. MeRs-coV=MIDdLe EasT respirAToRY SynDrOmE coRoNAvIrus. SaRS-coV=seveRe acute resPirAtOry syndrome cORoNavirus. Of tHe 41 pAtients in thiS coHort, 22 (55%) deVeLopED seveRe dYspnoEa and 13 (32%) rEQuired Admission To AN intenSIve care UNIt, And sIx died.Hence, the casE-FaTAlity proportioN in thiS cOHoRT Is aPprOximately 14·6%, aNd The ovERall casE FaTALIty PRoportion appeArs to be closER to 3% ( Table ). HOwEveR, Both of These EsTImaTes should be TreaTed with grEat cauTIon becaUSe not alL patieNts HavE conCLuDeD thEiR IllNEsS (ie, REcoVered or dIeD) aNd the True NUMBEr of InfEctiOns anD full disease sPecTrum ARe uNknowN. ImpoRtanTlY, in emErging Viral InFection outbreakS the Case-fatalIty RaTio Is Often OVerestImaTed In the eaRly stagES beCaUSE CaSe detection is highlY bIASeD towards The morE SeVeRE cases. As FuRthEr daTA On the SpecTRuM of mild oR asympTOmAtIc infecTiOn becoMeS avAilAble, oNE casE of whiCh was docUmentED by Chan and collEAgues,the case-fATaLITy RAtio Is lIkely to decrEase. nEverThelESs, The 1918 INflueNza paNdEMiC Is estimated to have haD a Case-faTalitY ratio of less tHan 5%but had aN ENOrmous imPact DUe TO widespread traNsmisSion, so therE Is no room For coMplacencY.

As an RNA vIRUs, 2019-nCoV stIll Has The InhEREnT feature of a hiGH MutaTiOn rate, aLthOugh likE otHer CorOnaViRuses the mUtation rAtE mIgHt Be sOmewhAT lower thAn OthEr rNA VirusES becauSe of iTs geNoMe-ENcoDed exonUClEASe. ThIs AsPect ProViDes thE posSIbiLity for This newly IntROducEd ZoOnotic vIral pathogen tO aDapt to becoMe MorE efficIENtly tranSmitted from person to persON and posSibLy becOme mOre viruleNt.

14 ZHong NS

zheNG BJ

Li Ym

et al. EPidemIoLogY ANd cauSE Of SevErE acute respIRAtoRy synDrOme (SaRS) in GuAngdong, People's RepuBLic Of China, in FebrUarY, 2003. 12 WHO

sUMmAry OF pRObaBlE sARs CAses with onset of Illness froM 1 NOVeMber 2002 to 31 July 2003. gEneVa: world HeAlth OrgAnizaTIon. Two pRevious coRonavirus OuTbreAKS haD been reporTed in the 21St century. tHe cliNIcAl feaTurEs of 2019-nCOV, In cOmparIson wiTH SArS-CoV And MidDlE East rEspirAtOry syndrOme (MERS)-CoV,
noea 22 (55%) 72% 40–42% D iarrhoea 1  (3%)  26 % 2 0– 25%Sore  throat 0 21%1 3–25 % Ventilatory support9·8%80 %  14– 2 0%  Data  are n, ag e (ra ng e) , o rn  ( %) un les s other wise state d.20 19-nCoV=2019 no vel corona vir us. MERS-CoV =Mi ddle E as t r e spira tor y syn dromec oronav irus. SAR S- C oV=sev e re acut e re spir atory syndrome co r on a virus. Of the41 pat ie n ts i n t his  cohort, 2 2(55%) develop e ds e v ere dyspnoea and13 (32%) re q uir ed adm is sio n  to an  inte ns i vecare unit,andsix died. Hence, the cas e -fatali ty pro por tio n in th is  co ho r t i s  a ppr o xim ately 14 ·6 %,  andtheo v e r allcas e fa talit y proportionapp ears tobe cl oserto 3 %( tab le ).Howev er , both of these  est imates sh oul dbetr eated with g rea t c autionbecause not  a l l pa tients have conclu de d th eir illn ess (i e ,re c overed o rdie d) a n d  thetrue nu mber ofinfect i on sand ful ldiseas espe ctr um ar e  unk nown.Importan tly,i n emerging vir a l infection o u tb r e ak s  the  ca se-fatality  rat i o is  oft e nove r estim atedin th e  early stages becau se  casedetec tion is highl y biased t o w a rds themore se v ere cases. Asfurth er data on the spec trumof mildor asympt o m atic inf ect ion  be com e s  a vailable, one c aseof  whichwas  docume nte d b y C han  a nd collea gues,the  c as e- fa tal ity r a tio is l ik ely  t o d ecrea s e. Nev erthe less ,th e  19 18 infl u en z a  pan de mi c is  es ti mated  toh ave  had acase-fata lit y  rat io  o f lessthan 5%but ha dan enormou simp act du e to wides pread transmission, sot here is  no  room  for  complace ncy .

AsanR NA vir us, 20 19-nC oV  st i l l has t he  in he rent featu r e  of  a hi gh  mut ation r ate, although like oth er coronaviru ses  the m ut ati o nr ate  m i ght b e somewhat lowe r than oth er RN A virusesb eca us e of it s genom e-enc o ded exo nuclease.  This asp ec t pr o v ide s the poss ibilityfor thisn ewlyi nt roduc edzoonot ic  vi ral p athoge n  to  adap t to b ec ome mo re ef fi cientlytransmitted from person  to pe rsonand  possibly  be c ome  more vir ulen t.

14 Zho ngNS
Zhen g B J 

LiYM
e tal. Epide miol o gy and ca u se  of s ev ere acute r e s p ira torysyn d rome ( SARS ) in Guangdong, P e ople's Republi c of C hin a,i n Fe br uary, 2003. 12  WH OS ummary o fprobable SA RS cases  w i th on set of  illne ss from 1  N o vember  200 2 t o 31 July  20 03 .  Geneva :Wo r ld Hea lthOr ganiza tion.T wo p r e vious coronaviru s out b r eaksh adbeenre portedi n th e 21st cen tury. The c linica l fe ature s of 20 19 -nCoV,  in  c omparisonw ith SARS- CoV a nd Midd le  Eas t r espira tory s yndro me ( ME RS) -CoV,
noea 22_(55%) 72%_40–42% Diarrhoea 1 (3%)_26% 20–25%_Sore_throat 0_21%_13–25% Ventilatory support_9·8% 80% 14–20%_Data are n, age_(range), or n_(%)_unless otherwise stated. 2019-nCoV=2019 novel coronavirus. MERS-CoV=Middle East respiratory syndrome coronavirus. SARS-CoV=severe acute respiratory_syndrome_coronavirus. Of_the_41_patients in this cohort, 22_(55%) developed severe dyspnoea and_13 (32%)_required admission to an intensive care unit, and_six_died.Hence, the case-fatality_proportion in this cohort is approximately 14·6%, and the_overall case fatality proportion appears to_be closer to_3%_(_table ). However, both_of these estimates should be treated_with great caution because not all_patients have concluded their illness (ie, recovered_or died) and the true number_of infections and full disease_spectrum are_unknown. Importantly, in emerging viral_infection outbreaks the_case-fatality ratio_is often overestimated_in the early stages because case_detection is highly_biased towards the more severe cases._As_further data on_the_spectrum_of mild_or asymptomatic infection_becomes_available, one_case_of which was documented by Chan_and_colleagues,the case-fatality ratio is likely to decrease._Nevertheless, the 1918 influenza_pandemic_is estimated to have_had a case-fatality ratio of_less than 5%but had an enormous_impact due_to widespread_transmission, so there is no room for complacency.

As an RNA virus,_2019-nCoV still has the inherent feature_of a high mutation_rate, although_like_other coronaviruses the_mutation_rate might_be somewhat lower than other RNA viruses_because of_its genome-encoded exonuclease. This aspect provides_the possibility for this_newly_introduced zoonotic viral pathogen to adapt_to become more efficiently transmitted from_person to person and possibly_become_more_virulent.

14 Zhong NS

Zheng BJ

Li YM

et_al. Epidemiology and cause of severe_acute respiratory syndrome_(SARS) in Guangdong, People's Republic of China,_in_February, 2003. 12 WHO

Summary of probable_SARS_cases with onset of illness from_1_November_2002 to 31 July 2003._Geneva: World Health Organization. Two previous_coronavirus outbreaks had been reported in the 21st century._The clinical features_of 2019-nCoV, in comparison with_SARS-CoV_and_Middle East respiratory syndrome (MERS)-CoV,