In the Turkish case there was a report in a US newspaper (NYTimes?) of trucks arriving in the town where the children died, carrying old broilers from a nearby factory that were sold off cheap. Not proof of anything, but a plausible way people could get infected ahead of backyard flocks.
I’m sure Devlin can help here: my understanding was [some at least] contract farms use chicks supplied by the big factory farms?
See below re Lhasa. Is that market a "wet" one?
But there’s a perfectly rational and obvious explanation: the pattern of spread goes from east to west following road and railway lines. Avian flus have been moved along railway lines before: 1925 in the USA for example. Dirty carrying crates were apparently the vector then. The spread across Eurasia doesn’t follow any bird migration pathway, nor is there any species that begins its migration in the east in spring and ends up in the west in autumn. Migration is a forward-backward movement: if the disease went north in spring, it would come back south in autumn.
But it’s very strange the disease hasn’t crossed from domestic free-range ducks to wild, migrant ducks (e.g. complete absence of the virus in healthy wild birds for the last decade at Mai Po). Shouldn’t wild bird populations be awash with the disease in Asia by now?
Again, there’s a perfectly rational explanation for this. One of the FAO bulletins reported that an outbreak in Lhasa, Tibet, in 2004 was traced back to Lanzhou, China, 1,500 km away. The outbreak was at the main poultry market in Lhasa. Suppose the birds had been sold to smallholders a day or two earlier at the market? Result: sudden, near simultaneous outbreaks in backyard farms across Tibet – precisely the pattern reported in e.g. the Ukraine. And where was the finger of blame pointed? Wild birds of course. And where is Lanzhou? A "hub" on the silk road, on a major railway line that runs from China to Eastern Europe.
I’m sure, therefore, you can understand our frustration when the popular belief is that wild birds are the sole spreaders of the virus. Sure they could be playing a part, but a very minor one at most.