Evolving faces of SARS-CoV-2 with the emergence of diverse variants

ABSTRACT

Since the emergence of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in December 2019, scientists have tracked five variants of concern (VOC) of SARS-CoV-2. The variants such as B.1.1.7 and B.1.617.2 primarily originated independently from the United Kingdom and India, respectively, and subsequently became dominant across the globe. The adaptability of these variants depends on their relative survival fitness to the positive selection pressure acting on them. Antiviral drugs and vaccine usage might act as a selective environment, thus, facilitating the positive selection resulting in the rapid emergence of new variants with higher fitness and survival value. The recently emerged VOC, the omicron variant (B.1.1.529), was first reported from South African samples, and it has a large number of mutations some of which are concerning as per the preliminary evidence. Owing to the dynamism of mutations in the SARS-CoV-2 genome, we may expect many unexpected events as far as the emergence of variants, virulence, and transmissibility is concerned. However, as an evolutionary trade-off strategy, the virulence of SARS-CoV-2 might get reduced with an increase in the transmissibility to attain a wider host range. The intermingling of vaccinated and unvaccinated individuals provides the virus opportunity to amplify by infecting the unvaccinated individuals and causing breakthrough infections. Moreover, the prevalence of different variants of SARS-CoV-2 has been different in different geographic zones as far as the cases and causalities are concerned. Sustained viral surveillance and monitoring with region-wise variant-specific preventive strategies are required to prevent and contain the outbreak of emerging variants of SARS-CoV-2.