Thursday, May 2, 2013

H7N9 unlikely to go into mallards

let me repeat this, since I keep seeing concerns that
H7N9 may go into wild birds.

Avian influenza in wild birds, especially mallards (not geese,gulls,) mutates its proteins
in the inner segments only rarely. Flu is in mallards mainly
waterborne and infects in the intestine.
Only in poultry or mammals it then mutates more (protein,6 inner segments).
Such poultry mutated viruses are then after a few decades
no longer compatible for mallards and similar waterfowl, the main reservoir
for avian influenza..
The protein=amino-acid mutation counts in  H9N2 in the 6 inner segments went like this:

1980: 01,02,04,--,00,--,00,01 A/duck/Potsdam/15/1980(H7N7)
2001: 09,07,12,--,06,--,12,23 A/chicken/Shanghai/10/2001(H9N2)
2013: 07,13,19,--,09,--,27,34 A/China/2013(H7N9)

H9N2 in this form is in East China since around the late 1990s.
But even the H9N2 from 2001 above was no longer found in wild birds.
I assume this is mainly due to the many mutations in the segments 7 and 8,
which grew further to 27+34 now. You hardly find such viruses in mallards.
So a spread of H7N9 which has the same inner 6 segments as H9N2,
in wild birds, seems therefore unlikely.



---------------------------------------
some more counts:

distance from the bird index:
OR:7,4,7,-,2,-,1,2
CA:8,5,8,-,4,-,3,6
QA:10,4,7,-,2,-,3,6
98:8,6,11,-,4,-,15,23
00:6,4,9,-,5,-,12,21
01:9,7,12,-,6,-,12,23
09:5,12,16,-,10,-,27,31
13:7,13,19,-,9,-,27,34

OR:A/Duck/HK/702/1979(H9N2)
QA:A/Duck/HK/702/1979-quail-adapted(H9N2)
CA:A/Duck/HK/702/1979-chicken-adapted(H9N2)
98:A/Chicken/Shanghai/F/1998(H9N2)
00:A/Chicken/Shanghai/3/2000(H9N2)
01:A/Chicken/Shanghai/10/2001(H9N2)
13:A/Index/2013(H7N9)
09:A/Index/poultry/East-China/2009(H9N2)


(edited 2013.05.02.12:00ET)

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