The origin of SARS-CoV-2: how, where and when did the virus emerge?
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The ongoing pandemic of COVID-19 has been holding the whole world in its grip for almost two years. Soon after the initial reports of an unknown lung disease, the cause was identified to be a novel coronavirus called SARS-CoV-2. The pandemic has influenced billions of lives, causing millions of deaths worldwide and the numbers are still rising. In order to prevent a virus outbreak with such global impact in the future, it is crucial to gain more knowledge about how viruses emerge in the human population. If the factors that influence the introduction of novel viruses to humans are known, we might be able to stop the emergence of novel viruses by intervening with these factors. The aim of this paper is to increase the understanding of the origin of SARS-CoV-2 by providing a thorough, unbiased review of the current literature on this topic. Three aspects of the virus’ origin are discussed: how, where and when this virus was introduced in the human population. Two main routes of emergence of the virus are currently being considered: through nature or in a laboratory. Previous coronavirus outbreaks in human history have been linked to animal-to-human transmission and hence have a natural origin, with bats being the most prevalent animal source. While related viruses have been found in nature, no animal source has yet been identified for SARS-CoV-2. Moreover, the unique features that are seen in the SARS-CoV-2 genome urge scientists to reconsider a laboratory origin of the virus. Several laboratories across the world have been working on coronaviruses for decades and state-of-the-art experimental techniques allow researchers to create viruses without leaving any traces of it being unnatural. Regarding the initial location and timing of the virus’ emergence, the consensus is that the pandemic began in Wuhan, China in December 2019. Outside of China, however, investigations from Europe and America have reported the prevalence of the virus before that period. These reports raise the question whether SARS-CoV-2 could have originated outside of China before December 2019. Overall, it is clear that the origins of SARS-CoV-2 remain a point of discussion. The literature overview and in-depth discussion presented here forms a basis for further research into the origin of SARS-CoV-2. With this study, we hope to contribute to increasing the preparedness for future virus outbreaks to prevent our lives from ever being locked-down again.