FIG 5.

The current ecosystem of avian influenza viruses in China. The diversity of avian influenza viruses is maintained primarily in the classic gene pool viruses of wild waterfowl (green circle). Industrial poultry farming (blue and pink circles) largely separates species, but wild and domestic ducks may interact and transmit viruses. Trading in live-poultry markets (funnel) brings different types of poultry together to facilitate the sharing and mixing of viruses, favoring the emergence of novel AIVs and interspecies transmission of viruses (arrows). The markets are the major contact point between humans and live poultry, and this leads to the transmission of viruses to humans. Improper management may lead to the transfer of viruses from chickens in LPMs to those in farms. The stroke weight of an arrow indicates the frequency of transmissions between different hosts, arrowheads show the direction, and dashed lines indicate sporadic transmissions.