Re virus persisting in Vietnam, even without vaccines:
Would this have been case without China as northern neighbour? China seems key place of origin and reservoir for H5N1 (with vaccination used before thumbs-up from FAO).
– H5N1(Z) in Vietnam surely came from China in first place; was it introduced only once, or continually?
Do domestic ducks really make a suitable “trojan horse” reservoir, especially given research showing H5N1 can evolve to less virulent forms even in domestic ducks? That is, if they were the key reservoir for Vietnam, shouldn’t H5N1 in the country have shifted more strongly away from the genotype Z?
What research has been done or is planned into movements of poultry and other captive birds between China and Vietnam; and indeed between these and other countries?