ABSTRACT
The novel coronavirus SARS-CoV-2 responsible for COVID-19 emerged from the city of Wuhan, China and created a public health emergency worldwide in just four months of duration, which was declared a pandemic by the World Health Organization (WHO) on March 11, 2020. The most common symptoms include fever, dry cough, fatigue, sputum production, loss of smell, and shortness of breath, and in severe cases disease may progress to pneumonia, multi-organ failure and death. The SARS-CoV-2 virus is a unique beta-coronavirus due to the presence of a polybasic cleavage site along with O-linked glycans and a receptor-binding domain (RBD) in the spike protein. There are several questions over its origin but an analysis of public genome sequence data from SARS-CoV-2 and related viruses favors a natural origin and has found no evidence that the virus was made in a laboratory or engineered. Population genetic analyses of SARS-CoV-2 genomes indicated two major types, i.e., L and S, defined by two different SNPs that show nearly complete linkage across the viral strains sequenced to date. Although the L-type (~70%) is more prevalent than the S-type (~30%), the S-type was found to be the ancestral version. Human intervention may have placed more severe selective pressure on the L-type, which might be more aggressive and spread more quickly. On the other hand, the S-type, which is evolutionarily older and less aggressive, might have increased in relative frequency due to relatively weaker selective pressure. Although a number of diagnostics tests have been developed, real-time PCR (RT-PCR) is considered as one of the most sensitive and specific laboratory tests for confirmatory diagnosis of COVID-19. As no specific therapeutics and vaccines are available, the pandemic of COVID-19 is posing a great threat for global public health. In this review, we have tried to present the current state of development in the COVID-19 pandemic to public health authorities and potential readers worldwide.
