I highly recommend the article posted on Amazon Kindle by Bill Gallaher. It is written for a lay audience, but packed with important information.
Most pertinent to the new outbreak:
nCoV has an insertion that adds a furin cleavage site - RRXR - at the boundary of S1and S2 in the spike precursor.
This is the same type of mutation that changes H5 influenza virus and other avian viruses into more pathogenic variants
Bottom line is a new furin site upstream of the fusion peptide in the HA makes H5 etc more fusogenic in more tissues.
Likely similar story in nCoV.
This furin site is not present in SARS-CoV or other bat viruses closely related to nCoV.
More complex in 1918 flu - a different mutation in a different protein - but enhanced cleavage also contributed to enhanced spread as well.
This novel insertion in nCoV adds a minipatch of o-linked glycans in the prefusion trimer. These glycans overlay the fusion peptide in the adjacent monomer of the trimer. The fusion peptide is likely to be a major neutralization epitope so this newly added minimucin patch probably makes a difference in virulence and at least perhaps will make it more challenging to develop a vaccine.
Both the new furin site and the o-linked glycans are unique features of nCoV and important. Haven’t see this picked up yet by anyone else.