re: flight paths... I started to investigate this recently, but quickly realised it was more data than I have capacity to process. So many species of birds with so many migration routes and stops on their way. So I've left that well alone and will stick to tracking the cases that are found

re: contact for bird deaths outside of US...
Defra has a helpline - this is a UK number: 08459 335577.
Not much help if you're elsewhere!

A quick 'net search shows that there isn't a definitive source for reporting of dead birds. I think it might be a case of the authorities not wanting every Tom, Dick and Harry reporting every dead bird. They would soon get overwhelmed.

I would think OIE or WHO or 'someone' needs to come up with an organised method of reporting. Maybe via local veterinarians? I wonder if veterinarians will be issued with these ultraquick testing kits that have been introduced?

/thinks, "must email that veterinarian I know...."