Meta-analysis and comprehensive study of coronavirus outbreaks: SARS, MERS and COVID-19

Abstract

Background: Zoonotic coronaviruses have caused several endemic and pandemic situations around the world. SARS caused the first epidemic alert at the beginning of this century, followed by MERS. COVID-19 appeared to be highly contagious, with human-to-human transmission by aerosol droplets, and reached nearly all countries around the world. A plethora of studies were performed, with reports being published within a short period of time by scientists and medical physicians. It has been difficult to find the relevant data to create an overview of the situation according to studies from accumulated findings and reports. In the present study we aimed to perform a comprehensive study in the context of the case fatality ratios (CFRs) of three major human Coronavirus outbreaks which occurred during the first twenty years of 21st century.

Methods: In this study, we performed meta-analyses on SARS, MERS and COVID-19 outbreak events from publicly available records. Study analyses were performed with the help of highly reputable scientific databases such as PubMed, WOS and Scopus to evaluate and present current knowledge on zoonotic coronavirus outbreaks, starting from 2000 to the end of 2020.

Results: A total of 250,194 research studies and records were identified with specific keywords and synonyms for the three viruses in order to cover all publications. In the end, 41 records were selected and included after applying several exclusion and inclusion criteria on identified datasets. SARS was found to have a nearly 11% case fatality ratio (CFR), which means the estimated number of deaths as a proportion of confirmed positive cases; Taiwan was the country most affected by the SARS outbreak based on the CFR analysis. MERS had CFRs of 35.8 and 26 in Saudi Arabia during the 2012 and 2015 outbreaks, respectively. COVID-19 resulted in a 2.2 CFR globally, and the USA reported the highest mortality ratio in the world in the end of first year of COVID-19 pandemic.

Conclusion: Some members of the Coronaviridae family can cause highly contagious and devastating infections among humans. Within the last two decades, the whole world has witnessed several deadly emerging infectious diseases, which are most commonly zoonotic in nature. We conclude that pre-existing immunity during the early stages of a pandemic might be important, but case control and management strategies should be improved to decrease CFRs. Finally, we have addressed several concerns in relation to outbreak events in this study.

Keywords: COVID-19; MERS; Meta-analysis; Outbreak; SARS.

Graphical abstract

Fig. 1

PRISM Flow diagram showing identification and selection of publications for review of outbreaks by meta-analysis.

Fig. 2

Info-graphic representation of transmission of SARS, MERS and COVID-19. Host and intermediary host along with R₀ among humans are shown for comparison.

Fig. 3

Info-graphic illustration of coronavirus (SARS, MERS and COVID-19) outbreak events in respective originating countries and dates of first occurrences.

Fig. 4

Graph representing calculated CFRs for SARS during 2002–2004 outbreaks from highly affected countries.

Fig. 5

Graph showing calculated CFRs for MERS outbreaks from highly affected countries.

Fig. 6

COVID-19 CFR status up to the last week of December 2020, since the first case was reported. Graphs bars represent continents (A–E) and some and highly affected selected countries with death vs. case numbers around the world. Total case and death numbers along with CFRs are included in the latest graph to summarize current pandemic situation in the world (F).

Fig. 7

Schematic presentation of infections by sex distributions among the outbreaks. Error bars represent standard errors of medians, and a two-tailed nonparametric t-test was performed to analyze significant differences with Gaussian distribution (*p < 0.05).