  Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a novel virus
of beta coronavirus genus originated in Wuhan, China in December 2019, resulted
in the pandemic spread of Corona Virus Disease 2019 (COVID-19) worldwide. This
genus also contains SARS-CoV (originated in China 2002-2003) and MERS-CoV
(found in Saudi Arabia 2012). The nucleotide sequences of SARS-CoV-2 is closer
to SARS-CoV (with approximately 80% identity) than to MERS-CoV. Despite these
similarities, SARS-CoV-2 has two main features over the other coronaviruses.
The first is the high contagious rate and the second is the immune response
evasion. The higher transmission ability makes this virus quickly spread
worldwide with a high mortality rate and more economic losses. This review will
provide an overview of the current knowledge on the role of some viral and host
cell factors in higher transmission and contagious spread of SARS-CoV-2.
