Saif Ali Khan Here is a site mentions why SARS-CoV-2 is more lethal than SARS (or SARS-CoV-1) [see below link]. You can see 2 papers in the link.
Why is SARS-CoV-2 spreading faster than its two ancestors? Why is SARS-CoV-2 lethal? Recent publications have shown that there are differences in their genome structure and immunological response to SARS-CoV-2 infection. The key markers involved in these interactions include Spike protein (S), Nucleocapsid (N), ACE-2 receptor, FURIN protease in addition to the cytokines.
Affinity of RBD for ACE2: The receptor-binding domain (RBD) of SARS-CoV-2 has a higher affinity for ACE2 than the RBDs from other coronaviruses. The higher the affinity, the more its ability to infect cells. Higher affinity may be because of a mutation in the RBD.
Polybasic furin cleavage site: In SARS-CoV-1, an additional polybasic cleavage site is found at the junction of S1 and S2 which allows effective cleavage by furin. This might have an impact on its transmissibility & pathogenesis.
Cytokine Profile: Cytokine profiles are often perturbed during viral infections. In individuals with SARS-CoV-2 infection, the level of inflammatory cytokines was significantly higher than normal. In addition, there was significant correlation between cytokine levels and severity of the disease. The severe cytokine storm is reflected in the severity of the symptoms. Find out which cytokines were affected.
Saif Ali Khan Look at this Nature paper (3/30/2020), to see how cunning this virus is. SARS-CoV-2 has evolved to become more vicious than its cousin, SARS (or SARS-CoV-1).
" Compared with the SARS-CoV-1 RBD (Recepter Binding Domain), a hACE2-binding ridge in SARS-CoV-2 RBD takes a more compact conformation; moreover, several residue changes in SARS-CoV-2 RBD stabilize two virus-binding hotspots at the RBD/hACE2 interface. These structural features of SARS-CoV-2 RBD enhance its hACE2-binding affinity to our cells. "
responsible for COVID-19, SARS-CoV-2, uses ACE-2 as an entry receptor. ... to be similar to the CoV that was responsible for the SARS pandemic that occurred in 2002. ... there have been outbreaks of severe, and sometimes fatal, respiratory illnesses that were later found to be caused by novel, human pathogenic CoVs.