gsgs
Registered User
most of our current seasonal flu is H3N1, other strains had become
extinct in the last pandemic in 1968.
So, almost all of human PB1 genes originate from that
one reassortment in China 1968.
Few reassortments or recombinations of PB1 with
entirely different PB1s from other viruses happened since then.
You can see below, how PB1 slowly acquired new mutations
and became more and more different from the original
PB1 from 1968.
Two viruses close in the picture can still be rather different,
from each other, they just only have both the same
distance from the 1968 pandemic virus.
You can see how in 1977 H1N1 was reintroduced and persists until
now with many differences to H3N2 in PB1 (and other
genes too, of course)
There is a large avian reservoir of different PB1 sequences,
this was not much reduced by the human 1968 pandemic.
the rate of climb decreases over time and the curves become less steep
because the possible locations for mutations become exhausted.
There are about 5-6 mutations in average per year in PB1 with 2200 nucleotides,
but most mutations are synonymous in only about 700 positions.
After 60-70 years half of these are exhauseted and new
mutations may come closer to HK/1/1968 as likely
as they increase the distance.
Important for immunity is HA, not PB1, and HA has only 1600 nucleotides.
You can argue, that the variability of mutations becomes somehow
exhausted after 50-100 years and maybe the virus becomes less competitive
as compared to new emerging/reassorting serotypes...
hmm, the blue pixels are still rising over time, thus mutating
away from 1968 PB1. Do they have a common origin ?
extinct in the last pandemic in 1968.
So, almost all of human PB1 genes originate from that
one reassortment in China 1968.
Few reassortments or recombinations of PB1 with
entirely different PB1s from other viruses happened since then.
You can see below, how PB1 slowly acquired new mutations
and became more and more different from the original
PB1 from 1968.
Two viruses close in the picture can still be rather different,
from each other, they just only have both the same
distance from the 1968 pandemic virus.
You can see how in 1977 H1N1 was reintroduced and persists until
now with many differences to H3N2 in PB1 (and other
genes too, of course)
There is a large avian reservoir of different PB1 sequences,
this was not much reduced by the human 1968 pandemic.
the rate of climb decreases over time and the curves become less steep
because the possible locations for mutations become exhausted.
There are about 5-6 mutations in average per year in PB1 with 2200 nucleotides,
but most mutations are synonymous in only about 700 positions.
After 60-70 years half of these are exhauseted and new
mutations may come closer to HK/1/1968 as likely
as they increase the distance.
Important for immunity is HA, not PB1, and HA has only 1600 nucleotides.
You can argue, that the variability of mutations becomes somehow
exhausted after 50-100 years and maybe the virus becomes less competitive
as compared to new emerging/reassorting serotypes...
hmm, the blue pixels are still rising over time, thus mutating
away from 1968 PB1. Do they have a common origin ?
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