Replication of SARS-CoV-2 in human respiratory epithelium

Aleksandra Milewska; Anna Kula-Pacurar; Jakub Wadas; Agnieszka Suder; Artur Szczepanski; Agnieszka Dabrowska; Katarzyna Owczarek; Marek Ochman; Tomasz Stacel; Zenon Rajfur; Pawel Piotr Labaj; Wojciech Branicki; Krzysztof Pyrc

Coronaviruses constitute a large family of RNA viruses that infect mainly mammals and 41 birds. In humans, there are four species associated with mild-to-moderate respiratory infections. 42 While these viruses are present in the human population for a long time, they are believed to 43 enter the human population in a zoonotic event, and one may speculate that they may have 44 caused epidemics similar to the one observed for the SARS-CoV-2. Time to the most recent 45 ancestor analysis suggests that human coronavirus HCoV-NL63 is the oldest species in humans, 46 followed by its cousin HCoV-229E and two betacoronaviruses, which emerged in humans in a 47 relatively near past 1, 2, 3, 4 . In the 21 st century, we already faced the emergence of the three novel 48 coronaviruses in humans, of which SARS-CoV disappeared after one season never to come 49 back, and MERS-CoV never fully crossed the species border, as its transmission between 50 humans is highly ineffective 5, 6, 7 . The 2019 zoonotic transmission, however, resulted in the 51 emergence of a novel human coronavirus, which seems to carry an optimal set of features 52 allowing for its rapid spread with considerable mortality. Whether the virus will become 53 endemic in humans is an open question 8, 9, 10 .