It's almost there is a invisible wall in the sky.
Something to do with the PCR Test that the US uses?
You show me the bird and I'll show you the positive PCR result.
Maybe we should do what they do, or Turkey, or.... That have some invisible protection
Actually, millions of birds in Mexico have been culled because of bird flu since the 1990s. The same can be said of birds in Canada, in Europe, in Africa, and in Asia. These events don't have the newsworthiness of bird culling in the US, so unless it is your job to track influenza outbreaks, you probably haven't heard of them.
Yes, it was my job to track outbreaks. I'm retired now, but I still pay attention.
The reason avian influenza keeps popping up all over the world is because of the migratory patterns of wild birds. Birds from the Eastern and Western hemisphere migrate to the poles during the summer, where they intermingle. This not only spreads influenza among the birds, it gives the influenza virus ample opportunities to mutate and become new strains of viruses. Because of their unique biology, influenza viruses are the most rapidly mutating viruses known.