From coronaviruses to coronaviruses

Abstract

The official history of the discovery of human coronaviruses dates back to 1965, when the first coronavirus B814, which has now been lost, was isolated on the organ culture of the trachea of a human embryo from the nasal swabs of a patient with acute respiratory disease. However, this date can only be an intermediate stage on its the long evolutionary path. Paleovirological studies have shown that coronaviruses could have appeared as early as the Stone Age - in the Upper Paleolithic era, and East Asia is called their place of origin a region that is well known to virologists as the source of many highly pathogenic influenza viruses and new coronaviruses, such as SARS-CoV, MERS-CoV, and SARS-CoV-2. This makes us take a different look at the seeming innocence of seasonal coronaviruses that circulated before 2002, when a human pathogenic virus appeared that caused SARS. This also fits well into the assumption about the coronavirus nature of the 1889 Russian flu pandemic. Today, four seasonal coronaviruses and three new, pathogenic for humans are known. Two seasonal coronaviruses (229E and NL63) belong to the genus Alphacoronavirus, 2 others (OC43 and HKU1) and three new coronaviruses (SARS, MERS and SARS-CoV-2) belong to the genus Betacoronavirus. In this review, we have focused on the extreme points seasonal coronaviruses and pandemic SARS-CoV-2. We tried to draw an analogy between them and identify the main features that distinguish them. From the point of view of epidemiology and clinic, they have in common only the airborne transmission route, characteristic of all respiratory viruses, and the ubiquitous distribution, the nature and intensity of which were not significantly affected by the influenza epidemics/pandemics. Seasonal coronaviruses continued to circulate even during the COVID-19 pandemic, when the majority of the other respiratory viruses had largely disappeared. Significant differences between seasonal coronaviruses and SARS-CoV-2 can be traced in the symptoms, severity and pathogenesis of the diseases they cause. At the structural level, they have a lot in common. These are taxonomic proximity, morphology, structure, physicochemical properties of virions, organization of the genome, the main stages of virus replication, etc. What made SARS-CoV-2 such aggressive? The few differences in the size of viral particles and viral genome that have been identified to date, the use or not of hemagglutinin esterase to penetrate the virus into a sensitive cell, attachment to different cell receptors cannot explain the significant difference in the severity of the infection caused by seasonal or pandemic coronavirus. Most likely, they are based on delicate molecular mechanisms that have yet to be discovered.