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Old 20th Aug 2021, 09:43
  #7646 (permalink)  
MickG0105
 
Join Date: May 2016
Location: Sunshine Coast
Posts: 1,148
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Originally Posted by Turnleft080
I have been trying to find info (maybe someone can) on the sudden disappearance of the Wuhan, Alpha, Beta, Gamma variants. On most graphs they are down to < 2%. Vaccines pretty march started at the beginning of the year so it wasn't the vaccines that kicked them out. Did the Delta variant just push them aside. ...
It's straightforward evolution, survival of the fittest, where fitness is measured in infectiousness.

The coronavirus has the potential to throw up a mutation every time it infects a cell and produces more of itself (ie. each 'generation'). Some of the mutations yield nothing in particular but every once in a while a mutation that changes the spike protein will make that variant more infectious. If that new variant is significantly more infectious and occurs in a relatively uninfected population, it's off to the races. Typically the more infectious variant outperforms its forebear and becomes the new dominant strain, initially in that population. The wonder of international air travel tends to be what connects a new variant to broader populations.

Thus when the 'original' Wuhan reached the UK that relatively uninfected population become the feedstock for the alpha-variant, about 50 percent more contagious than the original. In South Africa the original variant threw up the beta-variant, again about 50 percent more contagious than the original. Gamma probably first developed in South America but manifested itself in Japan. Delta appears to be one of the first variants on a variant, in that it almost certainly mutated from a non-original strain, likely alpha-variant, in the Indian population. It is estimated to be 60 percent more infectious than alpha and thus quickly dominated the previous dominant variant.

There's also been a raft of other variants - epsilon, zeta, eta, theta, etc - recorded that have bobbed in a specific sub-populations but that have either been not significantly more infectious than their forbear or emerged too late such that they couldn't achieve dominance.
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