Figure 1. Cumulatively identified cases of COVID-19 worldwide, as of 26 April, 2020 (WHO, 2020).
Virological characteristics of SARS-CoV-2
As previously mentioned, SARS-CoV-2, belonging to the coronaviridae family, is the causative pathogen of COVID-19. Closely resembled other β-CoVs, the SARS-CoV-2 virion with a genome size of ~3 kb has a nucleocapsid consisted of genomic RNA and phosphorylated nucleocapsid (N) protein (Jin et al., 2020). Of note, the nucleocapsid is embedded in a phospholipid bilayer and is encased by two disparate types of spike proteins: spike glycoprotein trimmer present in all coronaviruses and the hemagglutinin-esterase shared merely in some CoVs. The spike (S) protein plays a pivotal role in binding to receptors and is the key to determine host tropism and transmission capacity (Figure 2). The matrix protein (M) along with the viral envelop (E) are also located in the viral envelope (Wu et al., 2020b). Genome analysis showed that the SARS-CoV-2 possesses 5’ and 3’ terminal sequences, with a gene order 5’ -replicase open reading frame (ORF) 1ab-S-envelope(E)-membrane(M)-N-3’ (Lu et al., 2020). The virus particle is 60~100 nm in diameter and are round or oval (Xia et al., 2020a). It can be inactivated by ultraviolet light or heated at 56 °C for 30 min and is sensitive to most disinfectants (i.e., ether, 75% ethanol, peracetic acid, chlorine, as well as chloroform) (Kratzel et al., 2020).