The emergence of Covid-19: evolution from endemic to pandemic.

Human race has survived several outbreak of pandemics in the past and their impact was long lasting. Some of the recent pandemics have been caused by a viruses known as Coronaviruses (CoVs) which are diverse, complex, adaptable viruses that have a significant impact on human health and animal productivity. The novel coronavirus that emerged in Wuhan, China (SARS-CoV-2) in 2019 has quickly spread throughout the world. Human coronaviruses (HCoVs), including severe acute respiratory syndrome coronavirus (SARS-CoV) and 2019 novel coronavirus (2019-nCoV, also known as SARS-CoV-2), have led to a global epidemic with high morbidity and mortality. Human pathogenic coronaviruses, SARS-CoV and SARS-CoV-2, bind to their target cells through angiotensin-converting enzyme 2 (ACE2), which is expressed by epithelial cells of the lung, intestine, kidneys, and blood vessels. The efforts to contain the virus are undergoing throughout the world, given the many uncertainties regarding pathogen transmissibility and virulence. Thus, the ongoing studies to promote the understanding of HCoVs will help to avoid or/and minimize the impact of anticipated pandemics in future.