Contextualizing COVID-19 with the SARS and MERS Outbreaks

CONTEXTUALIZING COVID-19

Written by Victoria Comunale Illustrated by Megan Zou August 19, 2020

SARS AND MERS OUTBREAKS

When we grapple with the uncertainties of new experiences, we can often find comfort and familiarity by reflecting on the past. Although COVID-19 has brought a great deal of change to all of our lives, a global health scare caused by a coronavirus is something that we have dealt with before—granted, on a much smaller scale. Despite the seemingly endless news of skyrocketing case numbers and the novel challenges of rapid vaccine development, we are gradually piecing together an understanding of COVID-19. This knowledge of COVID-19 is in part formed by reflecting on similar diseases from the past: SARS (Severe Acute Respiratory Syndrome) and MERS (Middle East Respiratory Syndrome).

MERS, SARS, and COVID-19 are all respiratory diseases that have been at the center of public health crises. The underlying viruses that cause these diseases are all coronaviruses, which are a large subset of viruses that affect animals such as bats, camels, and cats and can evolve to infect humans [1]. The specific coronaviruses known to cause disease in humans are MERS-CoV, SARS-CoV, and SARSCoV-2, which cause MERS, SARS, and COVID-19, respectively [2]. Interestingly, the viruses that cause SARS and COVID-19 are so similar that the virus responsible for COVID-19 was named the second of its kind, SARS-CoV-2. Although SARS and MERS did not globally agitate societal norms and activities in the way that COVID-19 has, we can ground our perception of COVID-19 in our prior encounters with these viruses. So how does our situation compare to those of the past, and how can our experiences with previous coronaviruses help us today? It has become obvious that many nations were far underprepared for the pandemic that we are currently facing. There are at present over ten million cases worldwide which have resulted in over 600,000 deaths, and the numbers only keep climbing [3]. But unlike previous epidemics and pandemics, we are equipped with today’s advanced knowledge and technology. Not only do we have experience from dealing with previous coronaviruses, but technological progress over the past decade has also put us at an advantageous position with which to control the spread of the virus. For example, while it took months for the SARS genome to be sequenced, it took a matter of weeks for the COVID-19 genome [4].

While SARS and MERS are both respiratory illnesses caused by coronaviruses, nothing of this magnitude was experienced during those past outbreaks. SARS resulted in over 8,000 cases and 774 deaths mostly between the years 2003 and 2004 [5]. MERS resulted in 2,519 cases and 866 deaths mostly between the years 2012 and 2013, and about 80 percent of cases were localized in Saudi Arabia [5]. During these outbreaks, all non-essential travel was advised against, yet there were no widespread efforts put in place, such as mask-wearing and social distancing, to stop the spread of these viruses.

Although there were far fewer cases of SARS and MERS than of COVID-19, these diseases had higher mortality rates, with MERS having the highest: about one-third of cases resulted in deaths [5]. Like COVID-19, these previous viruses proved to be more fatal for the elderly: one study has found that SARS had a fatality rate of more than 50 percent for people 65 or older [6].

As we expand our understanding of COVID-19, we are learning that people with milder symptoms or those who are asymptomatic may be unknowingly infecting others with COVID-19. What we have observed is a virus as infectious as the flu, but much deadlier than the flu due to its effects on the lower respiratory tract [7]. While the majority of COVID-19 cases are luckily not as severe as cases of SARS or MERS, this comes with a downside: SARS and MERS were much easier to track and contain since most patients developed severe symptoms that were difficult to go undetected [7].

The average person infected with COVID-19 propagates the virus to about 2.0 to 2.5 people, while the average person infected with SARS propagated the virus to about 1.7 to 1.9 people [11]. Both R0 numbers, which gauge how contagious an infection is, are much higher than that of MERS, wherein the average person infected with MERS spread the virus to less than 1 person [11]. Because COVID-19 is much more contagious than either SARS or MERS, measures such as contact tracing which are used to effectively control the spread of the virus have only become more important [7]. During the SARS epidemic, practices such as isolating infected individuals and quarantining potentially infectious contacts were employed [8]. During the MERS epidemic, there was a rise in contact tracing efforts to track and isolate infected individuals in countries that were especially affected, such as South Korea [9]. These practices have been largely used during the COVID-19 pandemic, and countries that have already employed aggressive contact tracing and isolation tactics have surpassed other countries in “flattening the curve” [9].

While we are undoubtedly struggling to get the virus under control, many find hope in the promise of a vaccine. Cautiously optimistic forecasts predict that a vaccine will be developed within a year, as there are currently several potential candidates under consideration [1]. Although SARS and MERS caused global scares during their outbreaks, there still is no vaccine for either, which means that if either virus spreads from animal to human again, there is potential for another outbreak [4]. During both the SARS and MERS outbreaks, preventing spread of the disease was prioritized over the development of vaccines, which are costly to produce [4]. Although there are currently some vaccines in development for MERS, the project for a SARS vaccine was shelved in 2004 because by the time a potential candidate was developed, the outbreak was mostly contained [4]. On the other hand, developing a vaccine for COVID-19 is an extremely high priority for many research and government institutions. Simultaneously, many scientists have also advocated for the continuation of research into a MERS vaccine, given that MERSCoV appears to jump more easily from infected animals to humans than does SARS-CoV [4]. A recent study published in April of this year shows promising results for human trials of a MERS vaccine, with subsequent trials currently underway [10]. Ultimately, further exploration of potential MERS or SARS vaccines could also help inform our current efforts to find a vaccine for COVID-19.

Looking to our experiences with SARS and MERS, there is much that we have learned from the past that can inform our knowledge of SARS-CoV-2. At the same time, through further exploration of COVID-19, we may be able to advance our knowledge on all three of these coronaviruses. Hopefully, armed with this knowledge, we can reflect on our past, learn from our mistakes, and better prepare for our future.

REFERENCES[1] Coronaviruses. (2020, May 7). National Foundation for Infectious Diseases. https://www.nfid.org/infectious-diseases/ coronaviruses/

[2] Naming the Coronavirus Disease. (2020). World Health Organization. https://www.who.int/emergencies/diseases/ novel-coronavirus-2019/technical-guidance/naming-thecoronavirus-disease-(covid-2019)-and-the-virus-that-causes-it

[3] Maps & Trends. (2020) Johns Hopkins Coronavirus Resource Center https://coronavirus.jhu.edu/data

[4] SARS and MERS. (2020). Baylor College of Medicine. https://www.bcm.edu/departments/molecular-virology-andmicrobiology/emerging-infections-and-biodefense/specificagents/sars-mers

[5] COVID-19, MERS & SARS. (2020). NIH. https://www.niaid. nih.gov/diseases-conditions/covid-19

[6] Roos, R. (2003). Estimates of SARS death rates revised upward. CIDRAP. https://www.cidrap.umn.edu/newsperspective/2003/05/estimates-sars-death-rates-revisedupward

[7] Why is COVID-19 So Dangerous? (2020). UCI Health. https://www.ucihealth.org/blog/2020/04/why-iscovid19-so-dangerous

[8] Chew, S. (2007). SARS: how a global epidemic was stopped. Bulletin of the World Health Organization. https:// www.ncbi.nlm.nih.gov/pmc/articles/PMC2636331/

[9] Fisher M., Sang-Hun C.(2020). How South Korea Flattened the Curve. New York Times. https://www.nytimes. com/2020/03/23/world/asia/coronavirus-south-korea-flatten-curve.html

[10] German Center for Infection Research. (2020, April 22). Promising MERS coronavirus vaccine trial in humans. ScienceDaily. www.sciencedaily.com/releases/2020/04/200422132600.htm

[11] Petrosillo N;Viceconte G;Ergonul O;Ippolito G;Petersen E. COVID-19, SARS and MERS: Are they closely related? https://pubmed.ncbi.nlm.nih.gov/