Human coronaviruses (HCoVs)have long beenconsidered inconsequential pathogens, causing the“common cold” in otherwise healthy people. However,in the 21st century, 2 highly pathogenic HCoVs—severeacute respiratory syndrome coronavirus (SARS-CoV)and Middle East respiratory syndrome coronavirus(MERS-CoV)—emerged from animal reservoirs to causeglobal epidemics with alarming morbidity and mortal-ity. In December 2019, yet another pathogenic HCoV,2019 novel coronavirus (2019-nCoV), was recognized inWuhan, China, and has caused serious illness and death.The ultimate scope and effect of this outbreak is un-clear at present as the situation is rapidly evolving.Coronaviruses are large, enveloped, positive-strand RNA viruses that can be divided into 4 genera:alpha, beta, delta, and gamma, of which alpha andbeta CoVs are known to infect humans.1Four HCoVs(HCoV 229E, NL63, OC43, and HKU1) are endemicglobally and account for 10% to 30% of upper respira-tory tract infections in adults. Coronaviruses are eco-logically diverse with the greatest variety seen in bats,suggesting that they are the reservoirs for many ofthese viruses.2Peridomestic mammals may serve asintermediate hosts, facilitating recombination andmutation events with expansion of genetic diversity.
Common symptoms of SARS included fever, cough,dyspnea, and occasionally watery diarrhea.2Of in-fected patients, 20% to 30% required mechanicalventilation and 10% died, with higher fatality rates inolder patients and those with medical comorbidities.Human-to-human transmission was documented,mostly in health care settings. This nosocomial spreadmay be explained by basic virology: the predominanthuman receptor for the SARS S glycoprotein, humanangiotensin-converting enzyme 2 (ACE2), is found pri-marily in the lower respiratory tract, rather than inthe upper airway. Receptor distribution may accountfor both the dearth of upper respiratory tract symp-toms and the finding that peak viral shedding occurredlate (≈10 days) in illness when individuals were alreadyhospitalized. SARS care often necessitated aerosol-generating procedures such as intubation, whichalso may have contributed to the prominent nosoco-mial spread.Several important transmission events did occur inthe community, such as the well-characterized mini-outbreak in the Hotel Metropole in Hong Kong fromwhere infected patrons traveled and spread SARSinternationally. Another outbreak occurred at theAmoy Gardens housing complex where more than 300residents were infected, providing evi-dence that airborne transmission ofSARS-CoV can sometimes occur.4Nearly20 years later, the factors associated withtransmission of SARS-CoV, ranging fromself-limited animal-to-human transmis-sion to human superspreader events,remain poorly understood.
In 2012, another highly pathogenic beta-CoVmade the species jump when Middle East respiratorysyndrome (MERS) was recognized and MERS-CoV wasidentified in the sputum of a Saudi man who died fromrespiratory failure.3Unlike SARS-CoV, which rapidlyspread across the globe and was contained andeliminated in relatively short order, MERS has smol-dered, characterized by sporadic zoonotic transmis-sion and limited chains of human spread. MERS-CoVhas not yet sustained community spread; instead,it has caused explosive nosocomial transmissionevents, in some cases linked to a single superspreader,which are devastating for health care systems. Ac-cording to the World Health Organization (WHO)
While the trajectory of this outbreak is impossible to predict,effective response requires prompt action from the standpoint ofclassic public health strategies to the timely development andimplementation of effective countermeasures. The emergence ofyet another outbreak of human disease caused by a pathogenfrom a viral family formerly thought to be relatively benign under-scores the perpetual challenge of emerging infectious diseasesand the importance of sustained preparedness
REFERENCES
e Wilde AH, Snijder EJ, Kikkert M, van Hemert MJ.Host factors in coronavirus replication.Curr TopMicrobiol Immunol. 2018;419:1-42. doi:10.1007/82_2017_252.
de Wit E, van Doremalen N, Falzarano D,Munster VJ. SARS and MERS: recent insights intoemerging coronaviruses.Nat Rev Microbiol. 2016;14(8):523-534. doi:10.1038/nrmicro.2016.813.
Song Z, Xu Y, Bao L, et al. From SARS to MERS,thrusting coronaviruses into the spotlight.Viruses.2019;11(1):11. doi:10.3390/v110100594.
Yu IT, Li Y, Wong TW, et al. Evidence of airbornetransmission of the severe acute respiratorysyndrome virus.N Engl J Med. 2004;350(17):1731-1739.
doi:10.1056/NEJMoa0328675. Sheahan TP, Sims AC, Leist SR, et al.Comparative therapeutic efficacy of remdesivir andcombination lopinavir, ritonavir, and interferon betaagainst MERS-CoV.Nat Commun. 2020;11(1):222.doi:10.1038/s41467-019-13940-66.
Graham BS, Mascola JR, Fauci AS. Novel vaccinetechnologies: essential components of an adequateresponse to emerging viral diseases.JAMA. 2018;319(14):1431-1432. doi:10.1001/jama.2018.0345
Common symptoms of SARS included fever, cough,dyspnea, and occasionally watery diarrhea.2Of in-fected patients, 20% to 30% required mechanicalventilation and 10% died, with higher fatality rates inolder patients and those with medical comorbidities.Human-to-human transmission was documented,mostly in health care settings. This nosocomial spreadmay be explained by basic virology: the predominanthuman receptor for the SARS S glycoprotein, humanangiotensin-converting enzyme 2 (ACE2), is found pri-marily in the lower respiratory tract, rather than inthe upper airway. Receptor distribution may accountfor both the dearth of upper respiratory tract symp-toms and the finding that peak viral shedding occurredlate (≈10 days) in illness when individuals were alreadyhospitalized. SARS care often necessitated aerosol-generating procedures such as intubation, whichalso may have contributed to the prominent nosoco-mial spread.Several important transmission events did occur inthe community, such as the well-characterized mini-outbreak in the Hotel Metropole in Hong Kong fromwhere infected patrons traveled and spread SARSinternationally. Another outbreak occurred at theAmoy Gardens housing complex where more than 300residents were infected, providing evi-dence that airborne transmission ofSARS-CoV can sometimes occur.4Nearly20 years later, the factors associated withtransmission of SARS-CoV, ranging fromself-limited animal-to-human transmis-sion to human superspreader events,remain poorly understood.
In 2012, another highly pathogenic beta-CoVmade the species jump when Middle East respiratorysyndrome (MERS) was recognized and MERS-CoV wasidentified in the sputum of a Saudi man who died fromrespiratory failure.3Unlike SARS-CoV, which rapidlyspread across the globe and was contained andeliminated in relatively short order, MERS has smol-dered, characterized by sporadic zoonotic transmis-sion and limited chains of human spread. MERS-CoVhas not yet sustained community spread; instead,it has caused explosive nosocomial transmissionevents, in some cases linked to a single superspreader,which are devastating for health care systems. Ac-cording to the World Health Organization (WHO)
While the trajectory of this outbreak is impossible to predict,effective response requires prompt action from the standpoint ofclassic public health strategies to the timely development andimplementation of effective countermeasures. The emergence ofyet another outbreak of human disease caused by a pathogenfrom a viral family formerly thought to be relatively benign under-scores the perpetual challenge of emerging infectious diseasesand the importance of sustained preparedness
REFERENCES
e Wilde AH, Snijder EJ, Kikkert M, van Hemert MJ.Host factors in coronavirus replication.Curr TopMicrobiol Immunol. 2018;419:1-42. doi:10.1007/82_2017_252.
de Wit E, van Doremalen N, Falzarano D,Munster VJ. SARS and MERS: recent insights intoemerging coronaviruses.Nat Rev Microbiol. 2016;14(8):523-534. doi:10.1038/nrmicro.2016.813.
Song Z, Xu Y, Bao L, et al. From SARS to MERS,thrusting coronaviruses into the spotlight.Viruses.2019;11(1):11. doi:10.3390/v110100594.
Yu IT, Li Y, Wong TW, et al. Evidence of airbornetransmission of the severe acute respiratorysyndrome virus.N Engl J Med. 2004;350(17):1731-1739.
doi:10.1056/NEJMoa0328675. Sheahan TP, Sims AC, Leist SR, et al.Comparative therapeutic efficacy of remdesivir andcombination lopinavir, ritonavir, and interferon betaagainst MERS-CoV.Nat Commun. 2020;11(1):222.doi:10.1038/s41467-019-13940-66.
Graham BS, Mascola JR, Fauci AS. Novel vaccinetechnologies: essential components of an adequateresponse to emerging viral diseases.JAMA. 2018;319(14):1431-1432. doi:10.1001/jama.2018.0345
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