evidence that the 1918 pandemic started in America

[gsgs]

there had been speculation that the 1918 pandemic may have had
an early wave in France 1915 or 1916 or may have come
from China.

Avian influenza viruses of Eurasian and American type seem to
evolve separately since centuries and rarely intermix.

I made graphics of the distances of avian viruses to the 1918
pandemic virus for each of the 8 segments,
colored by Eurasian (black) and American (blue) type.

You can see how the blue dots are usually closer
to the bottom, thus phylogenetically closer to
the 1918 panflu-strain.
NP is somehow special.

Evolution in HA and NA is faster, in M slower than average.
In NS there are two very different lineages.

In PB1 and PA the 1918-virus is related to strains which
were clearly different to common strains but
rare (in birds) and apparantly also were rare in 1918.
H1 in birds is also not very common, so finding birds
with flu from times around 1918 will probably not match
1918-panflu in PB1,PA,HA but possibly in PB2.


The low dot in 2000 was a quail in Nanchang, which
caught a human virus.

[gsgs]

Re: evidence that the 1918 pandemic started in America

in the other two pandemics in the 20th century, 1957 and 1968
the actual human virus did acquire a new avian PB1 segment.
(together with HA,NA in 1957 ; together with HA in 1968)

Where did this PB1 come from ?
It looks as if both these PB1s were of American origin.
They are clearly closer related to current American
avian PB1s than to current Eurasian PB1s.

Closest match for PB1,1957(H2N2) is A/turkey/Wisconsin/1/1966(H9N2)
Closest match for PB1,1968(H3N2) is A/mallard duck/Alberta/57/1976(H5N2)


However these 2 pandemics did start in China !