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What came before? Comparison with other coronaviruses (MERS/SARS)

Overview of global threat coronavirus SARS and MERS
© COG-Train

In week 1, we covered the Great Influenza pandemic of 1918 and what we have learned since. As you will almost certainly have been aware before this course, the current pandemic is caused by a coronavirus, but this is not the first coronavirus outbreak in recent times. Severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) were discovered in the first and second decades of this century, respectively.

The first reported cases of SARS were in Foshun, China in November 2002. By February 2003, more than 300 cases had been reported with over a third of those in healthcare workers. By April 2003 WHO-led efforts had identified SARS-CoV as the causative agent of the disease. Owing to the infection control measures put in place, no further cases were identified after July 2003. Overall the pandemic ended with 8096 reported cases and 774 deaths across 27 countries.

MERS was first identified in June 2012, following the death of a man in Saudi Arabia from acute pneumonia and renal failure. In contrast to the SARS timeline, MERS-CoV was isolated from the sputum of this index case, demonstrating the advances in pathogen genomics during the intervening years. There was a cluster of travel-related cases in the UK in September 2012 and in 2015 a hospital related (nosocomial) outbreak in South Korea involving 16 hospitals and 186 patients, but the overwhelming majority of cases were observed in Saudi Arabia. As of January 2020 there had been 2,494 laboratory confirmed cases notified to WHO across 27 countries and resulting in 858 deaths.

Similarities between these two coronavirus outbreaks include the likely zoonotic origin (potentially from civets in a wet market for SARS and dromedary camels for MERS), and the high percentage of nosocomial cases involving both patients and healthcare personnel. This is likely due to the late peak viral shedding observed around 10 days after onset of infection, at which time individuals had already been hospitalised.

However, the case fatality rate was different in both pandemics – ~10% for SARS and ~36% for MERS. In the current pandemic, the unprecedented amount of testing, surveillance and tracing has led to a far greater ascertainment of cases. Despite the current case fatality rate being significantly lower than that of SARS and MERS, the absolute number of deaths is much higher, due to the global spread of SARS-CoV-2.

These previous coronavirus pandemics provided both genomic and clinical guidance in the early stages of the current pandemic.

In Figure 1, you can observe a timeline of previous pandemics and public health emergencies in history. The death toll of SARS-CoV-2 is significantly higher than the previous coronavirus epidemics SARS-CoV-1 and MERS. Learn more about the history of pandemics in this article from Visual Capitalist.

History of pandemics. A timeline illustrating previous pandemics. It shows the year of occurrence and the death toll. From highest to lowest death toll: Black Death (Bubonic plague) - 200 million deaths, year 1347-1351; Smallpox 56 million deaths, year 1520; Spanish flu - 40-50 million deaths, year 1918-1919; Plague of Justinian 30-50 million deaths, year 541-542; HIV/AIDS - 25-35 million deaths, year 1981-present; The Third Plague - 12 million deaths, year 1855; COVID-19, 5.4 million deaths, year 2019- 28Dec2021 (ongoing); Antonine Plague - 5 million deaths, year 165-180; 17th Century Great Plagues, year 1600; Asian flu - 1.1 million deaths, year 1957-1958; Russian flu - 1 million deaths, year 1889-1890; Hong Kong Flu - 1 million deaths, year 1968-1970; Cholera 6 outbreaks - 1 million deaths, year 1817-1923; Japanese Smallpox epidemic - 1 million deaths, year 735-737; 18th Century Great Plagues - 600 thousand deaths, year 1700; Swine Flu - 200 thousand deaths, year 2009-2010; Yellow Fever - 100-150 thousand deaths, year late 1800s; Ebola - 11.3 thousand deaths, year 2014-2016; MERS - 850 deaths, year 2012-present; SARS 770 deaths, year 2002-2003

Figure 1 – History of pandemics timeline. Source: Visual Capitalis.

© COG-Train
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The Power of Genomics to Understand the COVID-19 Pandemic

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