(Science News, July 2, 2020):
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(Referenced paper, June 26, 2020, by authors of previously referenced paper):
A SARS-CoV-2 variant carrying the Spike protein amino acid change D614G has become the most prevalent form in the global pandemic. Dynamic tracking of variant frequencies revealed a recurrent pattern of G614 increase at multiple geographic levels: national, regional and municipal. The shift occurred even in local epidemics where the original D614 form was well established prior to the introduction of the G614 variant. The consistency of this pattern was highly statistically significant, suggesting that the G614 variant may have a fitness advantage. We found that the G614 variant grows to higher titer as pseudotyped virions. In infected individuals G614 is associated with lower RTPCR cycle thresholds, suggestive of higher upper respiratory tract viral loads, although not with increased disease severity. These findings illuminate changes important for a mechanistic understanding of the virus, and support continuing surveillance of Spike mutations to aid in the development of immunological interventions. …
… Our data show that over the course of one month, the variant carrying the D614G Spike mutation became the globally dominant form of SARS-CoV-2. Phylogenetic tracking of SARS-CoV-2 variants at Nextstrain reveals complex webs of evolutionary and geographical relationships (nextstrain.org; Hadfield et al., 2018)); travelers dispersed G614 variants globally, and likely would have introduced and reintroduced G614 variants into different locations. Still D614 prevalent epidemics were very well established in many locations when G614 first began to appear. …
… Our global tracking data show that the G614 variant in Spike has spread faster than D614. We interpret this to mean that the virus is likely to be more infectious, a hypothesis consistent with the higher infectivity observed with G614 Spike-pseudotyped viruses we observed in vitro (Fig. 6), and the G614 variant association with higher patient Ct values, indicative of potentially higher in vivo viral loads (Fig. 5). Interestingly, we did not find evidence of G614 impact on disease severity; i.e., it was not significantly associated with hospitalization status. However, an association between the G614 variant and higher fatality rates has been reported in a comparison of mortality rates across countries, although this kind of analysis can be complicated by different availability of testing and care in different nations (Becerra-Flores and Cardozo, 2020).
While higher infectiousness of the G614 variant may fully account for its rapid spread and persistence, other factors should also be considered. These include epidemiological factors, as viral spread also depends on who it infects, and epidemiological influences can also cause changes in genotype frequency to mimic evolutionary pressures. In all likelihood, a combination of evolutionary selection for G614 and the founder’s effects of being introduced into highly mobile and connected populations may have together contributed in part to its rise. The G-clade mutations in the 5’ UTR, or in the RdRP protein might also have impact. In addition, there could be immunological consequences resulting from the G614 change in Spike.
Now I have to trawl through stuff myself to get updates 
