SARS, MERS and COVID-19: A Comparative Overview

SARS, MERS and COVID-19 are three major coronavirus diseases that have caused significant outbreaks in humans over the past two decades. Although they share similarities in their viral characteristics and clinical manifestations, they differ considerably in their transmissibility, disease severity, mortality and patterns of spread. The following table compares SARS, MERS and COVID-19 across key epidemiological, clinical, laboratory and virological characteristics.

Comparision of SARS, MERS and COVID-19

Feature	SARS	MERS	COVID-19
Causative Agent	SARS-CoV	MERS-CoV	SARS-CoV-2
Coronavirus group	Betacoronavirus	Betacoronavirus	Betacoronavirus
First emergence	2002, Guangdong/Foshan, China	2012, Middle East; first recognized case in Saudi Arabia	December 2019, Wuhan, China
Main animal reservoir / origin	Bats considered natural reservoir; palm civets implicated as an intermediate host	Bats considered probable natural reservoir; dromedary camels important intermediate host	Bat-related origin suggested; possible intermediate hosts were discossed, but the precise origin remained uncertain in the reviewed literature
Main cellular receptor	ACE2	DPP-4/CD26	ACE2
Genome similarity	SARS-CoV and SARS-CoV-2 share substantial genomic similarity; SARS-CoV-2 was reported to share ~79% of its genome with SARS-CoV	More distantly related to SARS-CoV-2 than SARS-CoV	Closely related to SARS-CoV; approximately 79% genomic similarity reported in the Frontiers review
Primary transmission	Mainly person-to-person respiratory transmission; substantial healthcare-associated transmission	Mainly healthcare-associated and close-contact transmission; outbreaks strongly associated with hospitals	Efficient person-to-person respiratory transmission with community and household spread
Typical incubation period	Generally around 2–10 days	Generally around 2–14 days	Generally around 2–14 days; several reviews report a median around 4–5 days
Common symptoms	Fever, dry cough, myalgia, headache; dyspnea and pneumonia in more severe disease	Fever, cough, dyspnea, myalgia, headache; gastrointestinal symptoms were relatively prominent	Fever, cough, fatigue/myalgia, headache and dyspnea; loss of smell/taste was also reported
Case fatality rate	~ 9-9.5%	~ 34-34.4%	~ 2-2.3%
Relative severity per infected person	High	Highest	Lower than SARS/MERS on a case-fatality basis
Geographical spread	Spread internationally but was eventually contained in 2003	Mostly Middle East with sporadi international outbreaks	Global pandemic
Major distinguishing feature	High severity and efficient transmission after symptom onset allowed containment	Very high fatality and strong healthcare/animal-associated transmission	Lower fatality but much greater community transmission including infections without obvious symptoms
Pandemic outcome	Outbreak contained in 2003	Did not develop into a global pandemic	Developed into a global pandemic

MERS had the highest reported fatality, SARS had substantial severity and healthcare-associated transmission, while COVID-19 had a considerably lower fatality rate but much greater ability to spread through the community.

Important interpretation

The most important epidemiological distinction is that high pathogenicity does not necessarily mean high pandemic potential.

• MERS had the highest case-fatality rate (~34%), but its transmission was relatively limited and strongly associated with healthcare settings.
• SARS had a substantial case-fatality rate (~9–9.5%) and spread internationally, but symptomatic transmission and effective infection-control measures contributed to its eventual containment.
• COVID-19 had a substantially lower early reported case-fatality rate (~2–2.3% in these papers), but its ability to spread efficiently in the community, including from people without obvious symptoms, allowed it to reach pandemic scale.

References

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Xie W, Wang Y, Xiong Y, Chen S, Han J, Wu Q. A comparative overview of COVID-19, MERS and SARS. Int J Surg. 2020;81:1-8. doi:10.1016/j.ijsu.2020.07.038.

Pustake M, Tambolkar I, Giri P, Gandhi C. SARS, MERS and CoVID-19: an overview and comparison of clinical, laboratory and radiological features. J Family Med Prim Care. 2022;11(1):10-17. doi:10.4103/jfmpc.jfmpc_839_21.

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Hu T, Liu Y, Zhao M, Zhuang Q, Xu L, He Q. A comparison of COVID-19, SARS and MERS. PeerJ. 2020;8:e9725. doi:10.7717/peerj.9725.

Guarner J. Three emerging coronaviruses in two decades: the story of SARS, MERS, and now COVID-19. Am J Clin Pathol. 2020;153(4):420-421. doi:10.1093/ajcp/aqaa029.

Petrosillo N, Viceconte G, Ergonul O, Ippolito G, Petersen E. COVID-19, SARS and MERS: are they closely related? Clin Microbiol Infect. 2020;26(6):729-734. doi:10.1016/j.cmi.2020.03.026.