History and Origin of Coronaviruses

ABSTRACT

Objective: The coronavirus disease 2019 (COVID-19) also known as COVID-19 or severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a viral infection caused by severe acute respiratory syndrome coronavirus 2, emerged first in Wuhan, China, and spread all over the world. The World Health Organization on January 30, 2020, officially declared the COVID-19 epidemic as a public health emergency of international concern. There is speculation as to the origin of the infection and the objective of this narrative review is to scan the available literature to create a cohesive review. Methodology: This review article is based on a literature search of PubMed, Google, and Google Scholar using the keywords " Corona virus," "COVID-19," "COVID" "Origins," "Review," and "classification." Articles providing new information were selected. Results: The coronavirus which has caused a pandemic has a genomic structure which closely resembles that of a bat coronavirus. The region that binds angiotensin-converting enzyme 2 (ACE2), i.e., the region of the spike proteins, resembles a coronavirus found in the pangolin (a scaly anteater found in the Chinese market and used in Chinese medicine). It is possible that the coronavirus was existing initially in its natural hosts, the bat, or pangolin. It is likely that the spike proteins mutated to bind to molecules similar to the human ACE2 protein therefore allowing it to infect humans. Another possibility is that it jumped species from bat to human and then became capable of causing pathogenic disease. The mutations in the receptor-binding domain portion of the spike protein and its distinct backbone, rules out laboratory manipulation as a potential origin for SARS-CoV-2. It is not certain if the necessary mutations for causing the pandemic occurred before or after SARS-CoV-2 made the jump to humans. Conclusions: The current corona pandemic is due to the SARS-CoV-2 and there is evidence that it has spread to humans from bats. Pangolins, civet cats may be reservoirs for the virus, but as of now, there is no evidence of a laboratory origin of the virus. It is not clear whether the virus jumped species recently or was preexisting in humans and became pathogenic because of a recent mutation.